AA	Affirmative Action committee
AA	Alcoholics Anonymous
AA	Automobile Association (in England)
AAA	American Automobile Association
AAAL	American Academy of Arts and Letters
AAAS	American Association for the Advancement of Science
ABA	American Bar Association
ABA	American Basketball Association
ABA	American Booksellers Association
ABC	American Broadcasting Company
AC	Alternating Current (ac, see also DC)
AC	Ante Christum (before Christ)
AC	Ante Cibum (before meals)
ACBL	American Contract Bridge League
ACD	Automatic Call Distributor [telephony]
ACE	Advanced Computing Environments [Corporate name]
ACE	Automatic Calibration and Equalization
ACM	Association for Computing Machinery
ACSE	Association Control Service Entity (ISO/CCITT layer 7)
ACTS	Advanced Communications Technology Satellite
ACTS	Automatic Coin Telephone Service  [telephony]
A/D	Analog to Digital converter (see ADC)
AD	Anno Domini (in the year of our Lord)
Ad Astra	To the stars [Latin; Space]
ADC	Analog to Digital Converter
ADF	Automatic Direction Finder
ADP	Adenosine Di-Phosphate
ADP	Advanced Data Processing
ADPCM	Pulse Code Modulation with Adaptive Quantization
ADT	Atlantic Daylight Time
AEC	Atomic Energy Commission
AEF	American Expeditionary Force (see BEF)
AF	Air Force
AF	Audio Frequency
AFB	Air Force Base
AFC	American Football Conference
AFC	Automatic Flight Control
AFC	Automatic Frequency Control
AFIPS	American Federation of Information Processing Societies
AFLCIO	American Federation of Labor and Congress of Industrial Organizations
AFSC	Air Force Systems Command
AFTRA	American Federation of Television and Radio Artists
AG	Adjutant General
AG	Attorney General
AHL	American Hockey League
AHQ	Air HeadQuaters
AI	Artificial Intelligence
AIAA	American Institute of Aeronautics and Astronautics
AID	Agency for International Development
AIDS	Acquired ImmunoDeficiency Syndrom
AL	American League (baseball)
ALA	American Library Association
ALA	Automobile Legal Association
ALBM	Air-to-Land Ballistic Missile
ALGOL	ALGOrithmic Language
ALS	Advanced Launch System [Space]
ALU	Arithmetic Logic Unit
AM	Amplitude Modulation
AM	Ante Meridiem (before noon)
AMA	American Medical Association
AMA	Automatic Message Accounting 
AMD	Advanced Micro Devices [Corporate name]
AMORC	Ancient Mystic Order Rosae Crucis
AMP	Adenosine MonoPhosphate
AMPAS	Acedemy of Motion Picture Arts and Sciences
AMRAAM	Advanced Medium Range Air-To-Air Missile
AMROC	American Rocket Company [Space]
AMSAT	radio AMateur SATellite corp.
AMU	Atomic Mass Unit
AMVET	AMerican VETeran
ANAC	Automatic Number Announcemnt Circuit [telephony]
ANC	All Number Calling [telephony]
ANC	Army Nurse Corps
ANG	Air National Guard
ANI	Automatic Number Identification [telephony]
ANSI	American National Standards Institute
ANZUS	Australia, New Zealand, United States
AOL	Absent Over Leave (see AWOL)
AOS	Alternate Operator Service [telephony]
A/P	Accounts Payable
AP	Associated Press
APB	All Points Bulletin
APO	Alpha Pi (?) Omega, service fraternity
APO	Army Post Office
A/R	Accounts Receivable
ARC	American Red Cross
ARCNET	Attached Resource Computer local area NETwork
ARO	After Receipt of Order
ARPA	Advanced Research Projects Agency (of the DoD, see DARPA)
ARRL	Amateur Radio Relay League
ARV	American Revised Version
ASAP	As Soon As Possible
ASCAP	American Society of Composers, Authors, and Publishers
ASCII	American Standard Code for Information Interchange
ASDIC	Anti-Submarine Detection Investigation Committee (British for sonar)
ASIC	Application Specific Integrated Circuit
ASN	Abstract Syntax Notation One (ISO/CCITT ASN.1)
ASSR	Autonomous Soviet Socialist Republic
AST	Atlantic Standard Time
ASV	American Standard Version
AT	Atlantic Time
ATA	Automatic Trouble Analysis 
ATC	Air Traffic Control
ATM	Automatic Teller Machine
ATP	Adenosine TriPhosphate
AT&T	American Telephone & Telegraph
ATTIS	American Telephone and Telegraph Information Systems
ATV	All Terrain Vehicle
AU	Astronomical Unit (93,000,000 miles) [Space]
AUS	Army of the United States
AUTODIN	AUTOmatic DIgital Network
AUTOVON	AUTOmatic VOice Network
AWACS	Airborne Warnings And Control Systems
AWK	al Aho, peter Weinberger, brian Kernighan (pattern scanning language)
AWOL	Absent WithOut Leave (also Absent Without Official Leave) (see AOL)
AXAF	Advanced X-ray Astrophysics Facility [Space]
BA	Bachelor of Arts
BARRNet	Bay Area Regional Research Network (SF Bay Area)
BASIC	Beginner's All-purpose Symbolic Instruction Code
BBC	British Broadcasting Corporation
BBN	Bolt, Beranek, and Newman [Corporate name]
BC	Before Christ
BC	British Columbia
BCD	Bad Conduct Discharge
BCD	Binary Coded Decimal
BCD	Binary Coded Decimal
BCDIC	Binary Coded Decimal Interchange Code
BCE	Before the Common Era (substitute for BC)
BCS	Bachelor of Commercial Science
BD	Bachelor of Divinity
BD	Bank Draft
BD	Bills Discounted
BE	Bill of Exchange
BEF	British Expeditionary Force (see AEF)
BELCORE	BELL COmmunications REsearch
BEM	Bug Eyed Monster
BENELUX	BElgium, NEtherlands, and LUXembourg
BER	Bit Error Rate
BERT	Bit Error Rate Test
BFA	Bachelor of Fine Arts
BHP	Brake HorsePower
BICS	Building Industry Consulting Services [telephony]
BID	Bis In Die (twice a day)
BIOS	Basic Input Output System
BiSync	Binary Synchronous Communications (BSC is preferred) [IBM]
Bit	BInary digiT
BITNET	Because It's Time Network
BLERT	BLock Error Rate Test
BLF	Busy Lamp Field [telephony]
BLT	Bacon Lettuce & Tomato
BM	Basal Metabolism
BM	Bowel Movement
BMA	Bank Marketing Association
BMR	Basal Metabolism Rate
BNC	Bayonet Neill Concelman (connector) [electronics] (see also TNC)
BO	Branch Office
BO	Buyer's Option
BOC	Bell Operating Company
BOQ	Bachelor Oficers' Quarters
BP	Blood Pressure
BP	British Petroleum
BP	British Pharmacopoeia
BPI	Bits Per Inch
BPOE	Benevolent and Protective Order of Elks
bps	Bits per second
BR	British Rail
BRS	Bibliographic Retrival Service
BS	Bachelor of Science
BS	Bill of Sale
BSA	Birmingham Small Arms
BSA	Boy Scouts of America
BSc	Bachelor of SCience
BSC	Binary Synchronous Communications (also sometimes BiSync) [IBM]
BSD	Berkeley Software Distribution
BSTJ	Bell System Technical Journal
BTAM	Basic Telecommunications Access Method [IBM]
BThU	British Thermal Unit (BTU {q.v.} is preferred)
BTL	Bell Telephone Laboratories
BTU	British Thermal Unit
BTW	By The Way [net jargon]
BWI	Baltimore-Washington Internationmal (airport)
BWI	British West Indies
BX	Base eXchange (see also PX)
CA	Chartered Accountant
CA	Chief Accountant
CA	Chronological Age
CA	Collision Avoidance (as in CSMA/CA (q.v.))
CAB	Civil Aeronautics Board
CACM	Communications of the Association for Computing Machinery
CAD	Computer Aided Design (sometimes seen as CAD/CAM)
CAE	Computer Aided Engineering
CAI	Computer Aided Instruction
CAM	Computer Aided Manufacturing (sometimes seen as CAD/CAM)
CAM	Content Addressable Memory
CAMA	Centralized Automatic Message Accounting
CAMTEC	Probably an ac.uk host address or user address therein
CAP	Civil Air Patrol
CATV	Common Antenna TeleVision
CATV	Community Antenna TeleVision
CAVU	Ceiling And Visability Unlimited
CBC	Canadian Broadcasting Corporation
CBD	Cash Before Delivery
CBS	Columbia Broadcasting System
CBW	Chemical and Biological Warfare
CC	Carbon Copy
CCA	Computer Corporation of America [Corporate name]
CCC	Canadian Committee on Cataloguing
CCC	Civil(ian) Conservation Corps
CCC	Command, Control, and Communications (sometimes C^3)
CCC	Concourse Computer Center [MIT]
CCCCM	CCC CounterMeasures (sometimes C^3CM)
CCCI	Command, Control, Communications, and Intelligence
CCD	Charge Coupled Device (see CID)
CCIS	Common Channel Interoffice Signaling [telephony]
CCITT	Comit\'e Consultatif International T\'el\'egraphique et T\'el\'ephonique
CCITT	Consultative Committee on International Telephony and Telegraphy
CCITT	International Telegraph and Telephone Consultative Committee
CCSA	Common Control Switching Arrangement [telephony]
CCTV	Closed Circuit TeleVision
CD	Carrier Detect (properly DCD (q.v.))
CD	Certificate of Deposit
CD	Civil Defense
CD	Collision Detection (as in CSMA/CD (q.v.))
CD	Compact Disk
CDC	Control Data Corporation, inc. [Corporate name]
CDR	CommanDeR
CDSF	Commercially Developed Space Facility
CDT	Central Daylight Time
CE	Chemical Engineer
CE	Civil Engineer
CE	Common Era (substitute for AD)
CE	Corps of Engineers
CE	Customer Engineer
CEA	Council of Economic Advisors
CEA	County Education Athority
CED	Committee for Economic Development
CELSS	Controlled Ecological Life Support System [Space]
CENS	Centre d'Etudes Nucleaires de Seclay
CENTO	CENtral Treaty Organization
CEO	Chief Executive Officer
CERN	organisation (formerly Conseil) Europeenne pour la Recherche Nucleaires
CF	Coin First payphone [telephony]
CFC	chlorofluorocarbon [chemical]
CFL	Canadian Football League
CG	Coast Guard
CHP	California Highway Patrol
CIA	Central Intelligence Agency [US Government]
CIC	Coordination and Information Center [CSNet]
CICS	Customer Information Control System [IBM]
CID	Central Institute for the Deaf
CID	Charge Injection Device (see CCD)
CID	Computer Integrated Design
CIM	Computer Integrated Manufacturing
Cislunar	The space between the Earth and the Moon
CIT	California Institute of Technology
CIT	Case Institute of Technology (part of CWRU, Cleveland, OH)
CIT	Circumstellar Imaging Telescope [Space]
CLU	Chartered Life Underwriter
CMOS	Complementary Metal Oxide Semiconductor (see MOS)
CMRR	Common Mode Rejection Ratio
CMSgt	Chief Master Sergeant
CN	Canadian National (railroad) [Corporate name]
CN/A	Customer Name / Address [telephony]
CNN	Cable News Network
CNO	Chief of Naval Operations
CNR	Canadian National Railways
CNR	Carrier to Noise Ratio
CO	Cash Order
CO	Central Office [telephony]
CO	Commanding Officer
CO	Conscientious Objector
C/O	in Care Of
COBOL	COmmon Business Oriented Language
COCOT	Customer Owned, Coin Operated Telephone [telephony]
COD	Collect On Delivery; Cash On Delivery
COMM	Communications
COMSAT	Communications Satellite [Space]
COS	Corporation for Open Systems
COSMIC	COmmon System Main InterConnecting frame
COSMOS	COmputer System for Mainframe OperationS
CP	Canadian Pacific
CP	Chemically Pure
CP	Command Post
CP	the Canadian Press
CPA	Certified Public Accountant
CPE	Customer Premises Equipment
CPE	Customer Provided Equipment
CPFF	Cost Plus Fixed Fee
CPM	Control Program Monitor (sometimes CP/M)
CPO	Chief Petty Officer
CPO	Chief Post Office
CPR	Canadian Pacific Railway
cps	Characters per second
CPT	CaPTain
CPU	Central Processing Unit
CRAF	Comet Rendezvous/Asteroid Flyby [Space]
CRC	Cyclic Redundancy Check
CRT	Cathode Ray Tube (terminal display)
CRTC	Canadian Radio-television and Telecommunications Commission
CS	Civil Servant
CS	Computer Science; Computing Science
CS	County Seat
CSA	Confederate States of America
CSMA	Carrier Sense Multiple Access
CSMA/CA	Carrier Sense Multiple Access with Collision Avoidance
CSMA/CD	Carrier Sense Multiple Access with Collision Detection
CSOC	Consolidated Space Operatons Center (at Colorado Springs)
CST	Central Standard Time
CSU	Channel Service Unit
CT	Central Time
CTC	Canadian Transport Commission
CTC	Centralized Traffic Control [railroad]
CTIO	Cerro Tololo Inter-american Observatory
CTV	Canadian TeleVision network
CUL	See You Later [net jargon]
CW	Chemical Warfare
CW	Child Welfare
CW	Churdwarden
CW	Continuous Wave
CWO	Cash With Order
CWO	Chief Warrant Officer
CWRU	Case Western Reserve University
CYO	Catholic Youth Organization
CZ	Canal Zone
D/A	Digital to Analog converter
DA	Directory Assistance (/C = computerized, /M = Microfilm)
DA	District Attorney
DA	Don't Answer [used in telephony, may be more general]
DAC	Digital to Analog Converter
DACCS	Digital Access Cross Connect System [telephony] (suspect, see below)
DACS	Digital Access Cross-connect System [telephony]
DAP	Division Advisory Panel [of NSF (q.v.) DNCRI (q.v.)]
DAR	Daughters of the American Revolution
DARPA	Defense Advanced Research Projects Agency
DATA	Defense Air Transport Administration
DAV	Disabled American Veterans
DB	DataBase
db	decibel(s)
dbms	DataBase Management System (rdbms for Relational ...)
DC	Direct Current (dc, see also AC)
DC	District of Columbia
DCA	Defense Communications Agency
DCD	Data Carrier Detect (sometimes CD (q.v.))
DCE	Data Communications Equipment
DDD	Direct Distance Dialing [Telephony; principally US, elsewhere STD]
DDN	Defense Data Network
DDS	Dataphone Digital Service [AT&T]
DDS	Digital Data Service
DDS	Direct Digital Service
DDS	Doctor of Dental Science
DDS	Doctor of Dental Surgery
DEC	Digital Equipment Corporation [Corporate name]
DEW	Distant Early Warning (as in DEW Line)
DF	Damage Free
D/F	Direction Finding
DF	Direction Finding
DFC	Distinguished Flying Cross
DFM	Distinguished Flying Medal
DFS	Depth-First Search
DFW	Dallas-Ft.Worth (regional airport)
DG	Data General [Corporate name]
DG	Dei Gratia (by the grace of God)
DG	Director General
DHHS	Department of Health and Human Services
DHSS	Department of Health and Social Security (British)
DID	Direct Inward Dialing [telephony]
DIS	Draft International Standard (eg ISO)
DIY	Do It Yourself
DJ	Disc Jockey
DLO	Dead Letter Office
DMA	Direct Memory Access
DMD	Doctor of Dental Medicine
DMF	Probably part of an X.400  address in Europe
DMOS	Diffussion Metal Oxide Semiconductor (see MOS)
DMV	Department of Motor Vehicles (Calif)
DMZ	DeMilitarized Zone
DNA	DeoxyriboNucleic Acid
DNA	Digital Networking Architecture [DEC]
DNCRI	[NSF (q.v.)] Division of Networking and Communications Research and Infrastructure
DNIC	Data Network Identification Code [telephony]
DNR	Dialed Number Recorder [telephony]
DOA	Dead On Arrival
DOB	Date Of Birth
DOD	Department of Defense
DoD	Department of Defense [U.S. Government]
DoE	Department of Energy [U.S. Government]
DOS	Disk Operating System
DOT	Department Of Transportation [U.S. Government]
DOV	Data Over Voice [telephony]
DP	Data Processing
DP	Dial Pulse [telephony]
DP	Displaced Persons (expelled from native land)
DP	Double Play
DRAM	Dynamic Random Access Memory (as opposed to static RAM)
DRG	Democratic Republic of Germany (East Germany)
DRI	Defense Research Internet
DRI	Digital Research, Incorporated [Corporate name]
DSM	Distinguished Service Medal
DSO	Distinguished Service Order
DSP	Decessit Sine Prole (died without issue)
DSP	Digital Signal Processing
DSS	Direct Station Selection [telephony]
DST	Daylight Saving Time
DSU	Digital Service Unit
DT	Delirium Tremens
DTE	Data Terminal Equipment
DTF	Dial Tone First payphone [telephony]
DTMF	Dial Tone Multi Frequency [telephony]
DTR	Data Terminal Ready
DUT	Device Under Test
DVM	Digital Volt Meter
DVM	Doctor of Veterinary Medicine
DWI	Driving While Intoxicated
DX	Distance (as in long distance radio communication)
E	East
EAN	Certainly part of an X.400 Address in Europe
EARN	European Academic Research Network
EBCDIC	Extended Binary Coded Decimal Interchange Code
EC	Exchange Carrier [telephony]
ECC	Error Correction Code (corrects error in memory or transmission)
ECCM	Electronic Counter-CounterMeasures
ECG	ElectroCardioGram
ECL	Emitter Coupled Logic (see also TTL)
ECLSS	Environmental Control and Life Support System [Space]
ECM	Electronic Counter Measure
ECM	European Common Market
ECMA	European Computer Manufacturers Association
ECO	Ecological
ECO	Engineering Change Order
ECT	ElectroConvulsive Therapy
ECV	Electric Cargo Vehicle [NASA OEXP]
EDI	Electronic Data Interchange
EDO	Extended Duration Orbiter [Space]
EDP	Electronic Data Processing
EDP	Electronic Data Processing
EDT	Eastern Daylight Time
EE	Electrical Engineer
EEC	European Economic Comunity
EEG	ElectroEncephaloGram
EEPROM	Electrically erasable Programmable Read Only Memory
EHF	Extremely High Frequency (30-300GHz)
EIA	Electronic Industries Association
EIA	Electronic Industry Association
EKG	ElectroKardioGramm (see ECG)
EL	ElectroLuminescent (as in display)
ELF	Extremely Low Frequency
ELV	Expendable Launch Vehicle [Space]
E&M	``Ear and Mouth''; receive and transmit leads of a signalling system
EMF	ElectroMotive Force
EMR	ElectroMagetic Response
EMT	Emergency Medical Technician
EMU	ElectroMagnetic Unit
EMU	Extravehicular Mobility Unit [Space]
EO	End Office [telephony]
EP	Extended Play
EPA	Environmental Protection Agency
EPROM	Erasable Programmable Read Only Memory
ER	Emergency Room
ERA	Earned Run Average
ERA	Equal Rights Amendment
ERT	Earth Resources Technology [Space]
ESA	European Space Agency
ESA	European Space Agency
ESE	East South East
ESF	Extended Superframe Format
ESM	Electronic Support Measures
ESO	European Southern Observatory
ESP	Extra Sensory Perception
ESS	Electronic Switching System [telephony]
EST	Eastern Standard Time
ET	Eastern Time
ET	External Tank [of the US Space Shuttle]
ET	Extra Terrestrial [Space]
ET	ExtraTerrestial
ETA	Estimated Time of Arrival
ET/ACC	External Tank/Aft Cargo Carrier (see also ET) [Space]
ETD	Estimated Time of Departure
ETFD	Electronic Toll Fraud Device [telephony]
ETO	Earth-to-Orbit [Space]
ETV	Education TeleVision
EVA	ExtraVehicular Activity
FA	Football Association (British soccer--a word derived from Association)
FAA	Federal Aviation Agency [U.S. Government]
FAO	Food and Agriculture Organization [U.S. Government]
FAX	FAcsimile
FBI	Federal Bureau of Investigation [U.S. Government]
FCC	Federal Communications Commission [U.S. Government]
FCCSET	Federal Coordinating Council for Science, Education and Technology (under OSTP)
FDA	Food and Drug Administration [U.S. Government]
FDDI	Fiber Digital Data Interface
FDDI	Fiber Distributed Data Interface
FDIC	Federal Deposit Insurance Corporation [U.S. Government]
FDM	Frequency Division Multiplexing
FET	Federal Excise Tax
FET	Field Effect Transistor
FFA	Future Farmers of America
FFT	Fast Fourier Transform
FG-A	Feature Group A [telephony:Line Side term. for LD carriers]
FG-B	Feature Group B [telephony:Trunk Side term. for LD carriers (aka ENFIA B), 950 service]
FG-D	Feature Group D [telephony:Trunk Side term. for LD carriers, 1+ service]
FICA	Federal Insurance Contributions Act
FIFO	First In First Out (as in registers and buffers)
FILO	First In Last Out (see also FIFO)
FLOP	FLoating point OPeration
FLOPS	FLoating-point OPerations per Second
FM	Frequency Modulation
FO	Foreign Office
FO	Forward Observer
FOB	Free On Board
FOC	Free Of Charge
FOR	Free On Rail
FORTRAN	FORmula TRANslation
FOT	Free On Truck
FOV	Field Of View
FPHA	Federal Public Housing Athority
FPLA	Field Programmable Logic Array (see PLA)
FPM	Feet Per Minute
FPO	Field Post Office
FPO	Fleet Post Office
fps	Feet Per Second
FRG	Federal Republic of Gernmany (West Germany)
FRS	Federal Reserve System
FSK	Frequency Shift Keying
FSLIC	Federal Savings and Loan Insurance Corporation
FTAM	File Transfer And Management (ISO upscale FTP)
FTC	Federal Trade Commission
FTP	File Transfer Protocol [esp. of the TCP/IP suite]
FTS	Federal Telecommunications System [US Government]
FTS	Federal Telephone System [telephony]
FTS	Flight Telerobotic Servicer [Space]
FUBAR	Fouled (other words work also) Up Beyond All Recognition
FX	Foriegn eXchange [telephony]
FYI	For Your Information
G	Gravity
GAAP	Generally Accepted Accounting Principles
GAB	Group Audio Bridging [telephony]
Gaia	Earth's self-sustaining Biosphere
GAR	Grand Army of the Republic
GATT	General Agreement on Tariffs and Trade
GAW	Guarenteed Annual Wage
GB	Great Britain
GC	Garbage Collection (LISP)
GC	Gas Chromatograph (or Chromatography)
GCR	Group-Coded Recording (magnetic tape, 6250 bpi)
GCT	Greenwich Civil Time
GEO	Geosynchronous Earth Orbit [Space]
GHQ	General HeadQuarters
GHz	Giga HertZ (unit of frequency, 1,000,000,000 cycles per second)
GI	Galvanized Iron
GI	Gastro Intestinal (as in upper GI)
GI	General Issue
GI	Government Issue
GIGO	Garbage In Garbage Out
GISS	Goddard Institute for Space Studies
GKS	Graphics Kernel System
GM	General Manager
GM	General Motors
GM	Guided Missile
GMT	Greenwich Mean Time
GNP	Gross National Product
GNU	GNU's Not Unix
GOSIP	Government Open Systems Interconnection Profile (calls for government procurement of ISO/CCITT products)
GP	General Practitioner
GPIB	General Purpose Interface Bus
GPO	General Post Office
GPO	Government Printing Office
GPS	Global Positioning System
GPS	Global Positioning System [Space]
GQ	General Quarters
GREP	Global Regular Expression Print [UNIX]
GRO	Gamma Ray Observatory [Space]
GSA	General Services Adminstration [U.S. Government]
GSA	Girl Scouts of America
GSFC	Goddard Space Flight Center (Greenbelt, MD) [NASA]
GT	Gross Ton
GTE	General Telephone and Electric [Corporate name]
HAL	Heuristically programmed ALgorithmic computer [movie 2001]
Hb	HemogloBin
HBM	Her British Majesty; His British Majesty
HBO	Home Box Office
HD	Heavy Duty
HDA	Head Disk Assembly (in winchester disk drives)
HDLC	High-level Data Link Control
HDTV	High Definition Television
HE	His Eminence; His Excellency
HEAO	High Energy Astronomical Observatory [satellite]
HEDM	High Energy-Density Matter [Space]
HEO	High Earth Orbit [Space]
HF	High Frequency (3-30MHz)
HLC	Heavy Lift Capability [Space]
HLV	Heavy Lift Vehicle [Space]
HMOS	High preformance Metal Oxide Semiconductor (see MOS)
HMS	His/Her Majesty's Ship
HNPA	Home Numbering Plan Area [telephony]
HOBIS	HOtel Billing Information System 
HOTOL	HOrizontal Take-Off and Landing
HP	Hewlett Packard, inc. [Corporate name]
HP	High Pressure
HP	HorsePower
HQ	HeadQuarters
HR	House of Representatives
HRH	Her Royal Highness
HRH	His Royal Highness
HS	High School
HST	Hawaiian Standard Time
HT	High Tension (as in electric power transmission)
HUAC	House Unamerican Activities Committee
HUD	Heads Up Display
HUD	Housing and Urban Development [U.S. Government]
Hz	HertZ (unit of frequency, cycles per second)
IAEA	International Atomic Energy Agency
IATA	International Air Transport Association
IBM	Ingrained Batch Mentality
IBM	International Business Machines [Corporate name]
IBM	Itty Bitty Machines
IC	Integrated Circuit
IC	Interexchange Carrier [telephony] (see also IEC)
ICBM	Intercontinental Ballistic Missile
IDDD	International Direct Distance Dial [telephony]
IDF	Intermediate Distributing Frame [telephony]
IDV	Interlibrational Derived Vehicle [Space]
IEC	Inter-Exchange Carrier [telephony] (see also IC)
IEEE	Institute of Electrical and Electronic Engineers
IF	Intermediate Frequency (as in IF stage)
IGY	International Geophysical Year
IHP	Indicated HorsePower
IIL	Integrated Injection Logic
ILO	International Labor Organization
ILS	Instrument Landing System
ILV	Industrial Launch Vehicle [Space]
IMF	International Monetary Fund
IMHO	In My Humble Opinion [net jargon]
IMP	Interface Message Processor [ARPANET/MILNET] (replaced by PSN)
INADS	INitialization and ADministration System  [telephony]
In-situ	In Place [Latin]
INWATS	INward Wide Area Telephone Service [telephony]
I/O	Input/Output
IOC	International Operating Center [telephony, US]
IOU	I Owe you(U)
IP	Information Provider [telephony]
IP	Innings Pitched
IP	Internet Protocol
IQ	Intelligence Quotient  (see EQ)
IR	Index Register
IR	Infra-Red
IRA	Individual Retirement Account
IRA	Irish Republican Army
IRAS	Infrared Astronomical Satellite
IRBM	Intermediate Range Ballistic Missile
IRDS	InfraRed Detection Set
IRE	Institute of Radio Engineers (old name for the now IEEE, which see)
IRS	Internal Revenue Service
IS	International Standard (Beyond the DIS Stage)
ISDN	Integrated Services Digital Network
ISEE	International Sun Earth Explorer (usually ISEE-3)
ISO	International Organization for Standardization 
ISODE	ISO Development Environment
ISPM	International Solar Polar Mission
ISRG	Independent Space Research Group
ITU	International Telecommunications Union
IUS	Inertial Upper Stage
IUS	Inertial Upper Stage [Space]
IUV	Interlibrational Utility Vehicle [Space]
JACM	Journal of the Association for Computing Machinery
JC	Jesus Christ
JC	Joint Compound (plumbing)
JC	Julius Caesar
JC	Junior College
JCAE	Joint Committee on Atomic Energy
JCEE	Joint Council on Economic Education
JCET	Joint Council on Educational Television
JCS	Joint Chiefs of Staff
JD	Justice Department
JFK	John F. Kennedy
JPL	Jet Propulsion Laboratory
JRC	Junior Red Cross
JSC	Johnson Space Center
JSRC	Joint Services Review Committee
JTIDS	Joint Tactical Information Distribution Systems
JV	Junior Varsity
JvNC	John von Neumann (Super Computer) Center
JvNCnet	John von Neumann (Super Computer) Center network
K9	canine (K9 corps - army dogs)
KC	King's Counsel (QC when queen reigning)
KC	Knights of Columbus
KERMIT	Kl-10 Error-free Reciprocal Micro Interconnect over Tty lines
KHz	Kilo HertZ (unit of frequency, 1000 cycles per second)
KP	Key Pulse [telephony]
KPNO	Kitt Peak National Observatory
KS	King's Scholar
KSC	Kennedy Space Center
KSU	Key System Unit [telephony]
KTS	Key Telephone System [telephony]
KTU	Key Telephone Unit [telephony]
L1	Lagrange Point #1 35,000 Miles above moon [Space]
L2	Lagrange Point #2 40,000 Miles behind moon [Space]
L3	Lagrange Point #3 (?? 35,000 Miles below moon) [Space]
L4	Lagrange Point #4 240,000 mile Earth orbit [Space]
L5	Lagrange Point #5 240,000 mile Earth orbit [Space]
LA	Los Angeles
LA	Low Altitude
LADAR	LAser Detection And Ranging
LAMA	Local Automatic Message Accounting [telephony]
LAN	Local Apparent Noon
LAN	Local Area Network
LAPB	Link Access Procedure (Balanced)
LASER	Light Amplification by Stimulated Emission of Radiation
LAT	Local Apparent Time
LATA	Local Access and Transport Area
LAX	Los Angeles International Airport
LBL	Lawrence Berkeley Labs
LBS	Pounds
LCD	Liquid Crystal Display
LCD	Lowest Common Denominator
LCL	Lunar Cargo Lander [NASA OEXP]
LCS	Laboratory for Computer Science [MIT]
LDC	Long Distance Carrier [telephony]
LDEF	Long Duration Exposure Facility
LDF	Large Deployable Reflector [Space]
LDX	Long Distance eXtender [telephony]
LEC	Local Exchange Carrier [telephony]
LED	Light Emitting Diode
LEM	Lunar Excursion Module
LEO	Low Earth Orbit [Space]
LF	Low Frequency (30-300KHz)
LH	Left Hand
LHD	Litterarum Humaniorum Doctor (doctor of human letters)
LHS	Left Hand Side
LI	Long Island
LIFO	Last In First Out (see FIFO)
LISP	LISt Processing Language
LL	Long Lines [telephony]
LLB	Legum Baccalaureus (bachelor of laws)
LLD	Legum doctor (doctor of laws)
LLN	Line Link Network [telephony]
LLO	Low Lunar Orbit [Space]
LLOX	Lunar Liquid Oxygen [Space]
LLP	Line Link Pulsing [telephony]
LM	Lunar Module
LMOS	Line Maintenance Operations System [telephony, AT&T]
LNG	Liquefied Natural Gas
LOFT	Launch Operations Flight Test [Space]
LOSF	Lunar Orbit Staging Facility [Space]
LOX	Liquid Oxygen
LP	Long Play(ing) (record)
LP	Low Pressure
LPC	Linear Predictive Coding (speech processing)
LPG	Liquefied Petroleum Gas
LPG	Low Pressure Gas
LPL	Lunar Personnel Lander [NASA OEXP]
LPN	Licensed Practical Nurse
LPT	Lunar Propellant Tanker [NASA OEXP]
LPV	Lunar Piloted Vehicle [NASA OEXP]
LRB	Liquid Rocket Booster [Space]
LRC	Longitudinal Redundancy Character
LRU	Least Recently Used
LRU	Line Replaceable Unit
LSB	Least Signficant Bit; Least Significant Byte
LSC	Lecture Series Committee [MIT]
LSD	Least Signficant Digit
LSD	LySergic acid Diethylamide
LSD	pounds (Libra), shillings (Sestertii), and (old) pence (Denarii)
LSI	Large Scale Integration
LTL	Less than Truckload Lot
LUG	Local Users Group
MA	Massachusetts [US state postal designation]
MACSYMA	project MAC's SYmbolic MAnipulation System
MAD	Mutual Assured Destruction
MADD	Mothers Against Drunk Driving
MAN	Metropolitan Area Network
MAP/TOP	Manufacturing Automation Protocol/Technical Office Protocol
MARBI	MAchine Readable form of Bibliographic Information
MARC	MAchine Readable card Catalog
MASER	Microwave Amplification by Stimulated Emission of Radiation
MASH	Mobile Army Surgical Hospital
MAST	Multi-Application SOnar Trainer
MBA	Master Business Adminstration
MC	Master of Ceremonies
MCSV	Mars Crew Sortie Vehicle [NASA OEXP]
MD	Doctor of Medicine
MD	Maryland [US state postal designation]
MDF	Main Distrbution Frame [telephony]
MDRE	Mass Driver Reaction Engine [Space]
ME	Mechanical Engineer
MEd	Master of EDucation
MeV	Million Electron Volts
MF	Medium Frequency (300-3000KHz)
MF	Multi-Frequency [telephony]
MFA	Master Fine Arts
MFLOPS	Million FLoating-point OPerations per Second (see also FLOPS)
MGM	Metro-Goldwyn Mayer [Corporate name]
MHD	MagnetoHydroDynamics
MHS	Mail Handling System [ISO]
MHz	Mega HertZ (unit of frequency, 1,000,000 cycles per second)
MI	Military Intelligence
MIA	Missing In Action
MILNET	MILitary NETwork
MIMD	Multiple Instruction, Multiple Data
MIPS	Million Instructions Per Second
Mir	Peace [Russian]
MIRV	Multiple Independently-Targetable Reentry Vehicle
MIS	Management Information System
MIT	Massachusetts Institute of Technology
MLL	Mars Logistics Lander [NASA OEXP]
MLV	Medium Lift Vehicle [NASA OEXP]
MMU	Manned Maneuvering Unit [Space]
MMU	Memory Management Unit
MMW	Multi-Mega Watt [Space]
MNP	Microcom Networking Protocol
MO	Mail Order
MO	Medical Officer
MO	Modus Operandi
MO	Money Order
MOMV	Manned Orbital Maneuvering Vehicle [Space]
MOS	Metal Oxide Semiconductor
MOSFET	Metal Oxide Semiconductor Field Effect Transistor
MOTV	Manned Orbital Transfer Vehicle [Space]
MOU	Memorandum Of Understanding
MOUSE	Minimum Orbital Unmanned Satellite of Earth
MP	Member of Parliament
MP	Metropolitan Police
MP	Military Police(man)
MPE	Mission to Planet Earth [Space]
MPG	Miles Per Gallon
MPH	Miles Per Hour
MPP	Member of Provincial Parliament (Canada; also MLA)
MPR	Mars Pressurized Rover [Space]
MPV	Mars Piloted Vehicle [NASA OEXP]
MS	ManuScript
MS	Master of Science
MS	Military Science
MS	Motor Ship
MS	Multiple Sclerosis
MSB	Most Signficant Bit; Most Significant Byte
MSD	Most Signficant Digit
MSG	MonoSodium Glutimate
MST	Mountain Standard Time
MT	Mountain Time
MTBF	Mean Time Between Failures
MTSO	Mobile Telephone Switching Office [telephony]
MTTR	Mean Time To Repair
MTV	Music TeleVision
MUNG	Mung Until No Good (see the hacker's dictionary)
MVA	MegaVolt Ampere
N	North
NA	North America
NA	Not Applicable
NAACP	National Association for the Advancement of Colored People
NAB	National Association of Broadcasters
NABISCO	NAtional BIScuit COmpany [Corporate name]
NAM	Name and Address Module [telephony, cellular phone changeable ROM]
NAM	National Account Manager [telephony, AT&T specific?]
NAM	Number Assignment Module [telephony, cellular phone changeable ROM]
NANP	North American Numbering Plan
NAS	National Academy of Sciences
NASA	National Areonautics and Space Administration
NASDA	National Space Development Agency [Japan]
NASP	National AeroSpace Plane
NATO	North Atlantic Treaty Organization
NB	New Brunswick
NB	Nota Bene
NBA	National Basketball Association
NBC	National Broadcasting Company
NBS	National Bureau of Standards (renamed NIST) [U.S. Government]
NC	No Charge
NC	No Connection
NC	North Carolina
NCO	Non-Commissioned Officer
NCR	National Cash Register [Corporate name]
NCSA	National Center for Supercomputing Applications
NCSC	National Computer Security Center
NCV	No Commercial Value
ND	North Dakota
NDEA	National Defense Education Act
NDSL	National Defense Student Loan
NDT	Newfoundland Daylight Time
NDV	NASP Derived Vehicle
NE	New England
NE	North East
NEARnet	New England Academic and Research Network
NEC	Nippon Electric Company [Corporate name]
NET	National Educational Television
NET	New England Telephone
NFC	National Football Conference
NFL	National Football League
NG	National Guard
NG	No Good
NHL	National Hockey League (the "nation" is Canada, BTW)
NHLBI	National Heart, Lung, and Blood Institute (Bethesda, MD)
NIC	Network Information Center
NIFTP	(a file transfer network in the UK)
NIH	National Institute of Health
NIH	Not Invented Here
NIMH	National Institute of Mental Health (Rockville, MD)
NIST	National Institute for Standards and Technology [U.S. Government]
NJ	New Jersey
NL	National League (baseball)
NLRB	National Labor Relations Board
NM	New Mexico
NMOS	N channel Metal Oxide Semiconductor (N-MOS) (see MOS)
NMR	Nuclear Magnetic Resonance
NNE	North North East
NNW	North North West
NORAD	NORth American Defense Command (?)
NP	No Protest
NP	Nondeterministic-Polynomial
NP	Notary Public
NP	Noun Phrase
NPA	Numbering Plan Area, or area code [Telephony]
NPC	Non-Player Character (see PC)
NPL	National Physical Laboratory (UK)
NPN	Negative-Positive-Negative (transistor)
NPN	NonProtein Nitrogen
NPR	National Public Radio
NRA	National Rifle Association
NRC	National Research Council
NRL	Naval Research Labs
NRZ	Non-Return to Zero
NRZI	Non-Return to Zero Inverted (magnetic tape, 800 bpi)
NS	Nova Scotia
NSA	National Security Agency [U.S. Government]
NSC	National Security Council [U.S. Government]
NSF	National Science Foundation [U.S. Government]
NST	Newfoundland Standard Time
NSTS	National Space Transportation System [Space]
NSW	New South Wales (Australia)
NTSB	National Transportation Safety Board [U.S. Government]
NUSC	Naval Underwater Systems Center [U.S. Government]
NW	North West
NWT	North West Territories (Australia)
NXX	NANP syntax for a three-digit string, {[2-9],[0-9],[0-9]} [Telephony]
NY	New York
NYC	New York City
NYSE	New York Stock Exchange
NYSERNet	New York State Educational and Research Network
NZ	New Zealand
OA	Office Automation
OAS	Organization Of American states
OBE	Order of the British Empire
OC	Order of Canada
OCLC	Online Computer Library Center, Inc.
OCS	Officer Candidate School
OED	Oxford English Dictionary
OEM	Original Equipment Manufacturer
OEO	Office of Economic Opportunity
OES	Order of the Eastern Star
OEXP	Office of Exploration [NASA]
OMS	Orbital Maneuvering System
OMV	Orbital Maneuvering Vehicle
OMV	Orbital Maneuvering Vehicle [Space]
ONI	Office of Naval Intelligence
ONI	Operator Number Identification [telephony]
ONR	Office of Naval Research
OPEC	Organization of Petroleum Exporting Countries
OR	Operating Room
OSC	Orbital Sciences Corporation [Space]
OSCAR	Orbiting Satelite Carry Amateur Radio (1st launched 12 Dec 1961)
OSF	Open Systems Foundation
OSF	Order of St. Francis
OSI	Open Systems Interconnection (per ISO 7 layer model)
OSS	Office of Strategic Services (later CIA)
OSS	Operation Support System [telephony, AT&T?]
OSTP	(White House) Office of Science and Technology Policy
OTV	Orbital Transfer Vehicle [Space]
OUTWATS	OUTward Wide Area Telephone Service [telephony]
OV	Orbiter Vehicle [Space]
PA	Per Annum
PA	Power of Attorney
PA	Press Agent
PA	Private Account
PA	Public Address
PA	Purchasing Agent
PABX	Private Automatic Branch eXchange [telephony]
PACX	Private Automatic Computer eXchange
PAD	Packet Assembler/Disassembler
PAM	Payload Assist Module [Space]
PBS	Public Broadcasting System
PBX	Private Branch eXchange [telephony]
PC	Personal Computer [IBM wants you to believe a specific kind]
PC	Player Character (see NPC)
PCB	PolyChlorinated Biphenyls
PCB	Printed Circuit Board
PCM	Pulse Code Modulation
PDP	Programmed Data Processor [DEC]
PDQ	Pretty Damned Quick
PDT	Pacific Daylight Time
PE	Phase Encoded
PHS	Public Health Service
PLA	Programmable Logic Array
PLL	Phase Lock Loop
PLO	Palestine (sic?) Liberation Organization (?)
PLO	Please Leave On
PM	PayMaster
PM	Police Magistrate
PM	Post Meridiem (after noon)
PM	PostMaster
PM	PostMortem
PM	Preventive Maintenance
PM	Prime Minister
PM	Provost Marshal
PMO	Prime Minister's Office
PMOS	P channel Metal Oxide Semiconductor (P-MOS) (see MOS)
PMT	PhotoMultiplier Tube
PN	Promissory Note
PNP	Positive-Negative-Positive (transistor)
PO	Petty Officer
PO	Post Office
PO	Postal Order
PO	Purchase Order
POP	Point of Presence [telephony]
POTV	Personnel Orbit Transfer Vehicle [Space]
POW	Prisoner Of War
PPB	Parts Per Billion
PPCS	Person to Person, Collect, Special [telephony]
PPM	Parts Per Million
PPN	Project Programmer Number
PPT	Parts Per Trillion
PPT	Punched Paper Tape
PQ	Province of Quebec
PR	PayRoll
PR	Public Relations
PR	Puerto Rico
PREPnet	Pennsylvania Research & Economic Partnership Network
PROM	Programmable Read-Only Memory
PS	PostScript
PS	Public School
PSC	Pittsburgh Supercomputer Center
PSDS	Public Switched Digital Service [telephony, AT&T?]
PSK	Phase Shift Keying
PSS	(unknown to me, but something in the UK environment)
PST	Pacific Standard Time
PT	Pacific Time
PT	Patrol Torpedo (as in PT boat)
PT	Physical Therapy
PT	Physical Training
PTA	Parent-Teacher Association
PTN	Plant Test Number [telephony:actual number assigned for 800 service]
PTO	Please Turn Over
PTT	Post, Telephone and Telegraph administration
PTV	Passenger Transport Vehicle [Space]
PVO	Pioneer Venus Orbiter
PX	Post eXchange (see also BX)
QC	Queen's Counsel
QED	Quod Erat Demonstrandum (which was to be demonstrated)
QEF	Quod Erat Faciendum (which was to be done)
QEI	Quod Erat Inveniendum (which was to be found out)
RA	Regular Army
RA	Research Assistant
RA	Royal Academy
RAAF	Royal Australian Air Force
RADAR	RAdio Detection And Ranging
RADM	Rear ADMiral
RAF	Royal Air Force
RAM	Random Access Memory (R/W)
RARE	Research Academic R(something) Europe (a Research Network)
RBI	Runs Batted In
RBOC	Regional Bell Operating Company
RC	Red Cross
RC	Resistor-Capacitor circuit (as in filters)
RC	Roman Catholic
RCAF	Royal Canadian Air Force
RCMP	Royal Canadian Mounted Police
R&D	Research and Development
REA	Rail Express Agency
RECON	Reconnaissance
REM	Rapid Eye Movement
RF	Radio Frequency
RFC	Request For Comments (ala ARPA Internet)
RFI	Radio Frequency Interference
RFP	Request for Proposal
RFQ	Request for Quote
RH	Right Hand
RHC	Regional (Bell) Holding Company
RHS	Right Hand Side
RIACS	Research Institute for Advanced Computer Science (NASA)
RIF	Reading Is Fundamental
RIP	Rest In Peace (or Requiescat In Pace : latin)
RISC	Reduced Instruction Set Computer
RJE	Remote Job Entry [IBM]
RLG	Research Libraries Group
RLIN	Research Libraries Information Network [run by RLG (q.v.)]
RLL	Run Length Limited
RMATS	Remote Maintenance Admistration and Traffic System [telephony]
RMS	Remote Manipulator System [Space]
RMS	Root Mean Square
RN	Registered Nurse
RN	Royal Navy
RNA	RiboNucleic Acid
RNZAF	Royal New Zealand Air Force
ROM	Range Of Motion (medical)
ROM	Read-Only Memory
ROM	Rupture Of Membrane (as in birth)
ROSE	Remote Operations Service Entity (per ISO/CCITT layer 7)
ROTC	Reserve Officers' Training Corps
RPG	Role Playing Game
rpm	Revolutions per minute
RPN	Reverse Polish Notation
RPO	Railway Post Office
RPS	Revolutions Per Second
RPV	Remotely Piloted Vehicle
RR	RailRoad
RR	Rural Route
RRO	Rate and Route Operator [telephony]
RSCS	Remote Spooling Communications Subsystem
RSFSR	Russian Soviet Federated Socialist Republic
RSVP	Repondez S'il Vous Plait (please reply)
RTAC	Regional Technical Assistance Center [telephony]
RTFM	Read The @!# Manual
RTTY	Radio Teletype
S	South
SA	SOuth Africa
SA	South America
SAA	South Atlantic Anomaly
SAC	Special Area Code [telephony:Area codes that are services, not places]
SAC	Strategic Air Command [US military]
SADD	Students Against Drunk Driving
SAM	Surface to Air Missile
SAMA	Step-by-step Automatic Message Accounting [telephony]
SASE	Self-Addressed Stamped Envelope
SAT	Satellite [Space]
SBA	Small Business Administration
SC	Secondary Channel
SC	South Carolina
SCUBA	Self Contained Underwater Breathing Apparatus
SD	South Dakota
SDI	Stategic Defence Initiative
SDI	Strategic Defense Initiative [US Government]
SDLC	Synchronous Data Link Control [IBM]
SDM	Sub-rate Data Multiplexer
SDSC	San Diego Supercomputer Center
SDV	Shuttle Derived Vehicle [Space]
SE	South East
SEATO	SouthEast Asia Treaty Organization
SEC	Security Exchange Commission
SEM	Scanning Electron Microscope
SETI	Search for Extra Terrestrial Intelligence [Space]
SF	San Francisco
SF	Science Fiction; Speculative Fiction
SHF	Super High Frequency (3-30GHz)
SIMD	Single Instruction, Multiple Data
SIRTF	Space Infrared Telescope Facility [Space]
Skyhook	Surface to space "elevator" transportation system [Space]
SL	Space Launch [Space]
SLBM	Submarine Launched Ballistic Missiles
SLC	Space Launch Complex [Space]
SLP	Super Long Play (VHS VCR)
SM	Service Mark
SMD	Storage Module Device (interface standard for disk drives)
SMD	Surface Mounted Devices
SMDR	Station Message Detail Recording
SMM	Solar Maximum Mission (satellite 1980-1989)
SMTP	Simple Mail Transfer Protocol
SNA	Systems Network Architecture [IBM]
SNAFU	Situation Normal -- All Fouled Up (also more profane versions)
SNCF	Societe National des Chemins de Fer (French National Railways)
SNOBOL	StriNg Oriented symbOLic Language
SNR	Signal to Noise Ratio
SOH	Start Of Header, ASCII contol character (dec=01,control-A)
SOHIO	Standard Oil of oHIO [Corporate name]
SOL	Short on Landing (or, colloquially, Shit Out of Luck)
Sonar	SOund Detection And Ranging
SOP	Standard Operating Procedure
SOS	Save Our Souls (International standard distress call, Morse ...---...)
SOS	Silicon On Saphire
SP	Shore Patrol
SP	Southern Pacific (railroad) [Corporate name]
SP	Stack Pointer
SPCA	Society for the Prevention of Cruelty to Animals
SPS	Solar Power Satellite [Space]
SRB	Solid fuel Rocket Booster
SRB	Solid Rocket Booster [Space]
SRI	Stanford Research Institute
SRO	Standing Room Only
SSA	Social Security Administration [U.S. Government]
SSB	Single Side Band
SSE	South-SouthEast
SSI	Small Scale Integration
SSI	Space Services Incorporated [Space]
SSPS	Satellite Solar Power Station [Space]
SSR	Soviet Socialist Republic
SSTO	Single Stage to Orbit [Space]
SSTV	Slow Scan TeleVision
SSW	South-SouthWest
STD	Sexually Transmitted Disease (replaces VD)
STD	Subscriber Trunk Dialing [British, and elsewhere; equiv. DDD in USA]
STL	St. Louis (airport designation)
STOL	Short TakeOff and Landing
STP	Standard Temperature and Pressure (see NTP)
STV	Space Transfer Vehicle [Space]
SUN	Stanford University Network
SUN	SUN MicroSystems Computer [Brand name]
SUNOCO	SUN Oil COmpany [Corporate name]
SURAnet	Southeastern Universities Research Association Network
SW	South West
SXS	Step by Step switching [Telephony]
T1	1.544Mbps [telephony], one of the basic signalling systems 24x64Kb
T3	45Mbps (eq 28 T1 channels) [Telephony]
TA	Teaching Assistant
TAC	Tactical Air Command (see SAC)
TAC	Terminal Access Controller [ARPAnet/MILNET/DDN]
TAU	Thousand Astronomical Units [Space]
TB	TuBerculosis
TBA	To Be Announced
TBD	To Be Determined
TBD	To Be Determined
TCA	Terminal Controlled Airspace
TCP/IP	Transmission Control Protocol/Internet Protocol
TD	TouchDown
TD	Treasury Department
TDM	Time-Division Multiplexer
TDRS	Tracking and Data Relay Satellite [Space]
Teflon	- polyTEtraFLuOrethyleNe
TIA	Thanks In Advance [net jargon]
TLC	Tender Loving Care
TM	TradeMark
TMA	Tycho Magnetic Anomaly [movie 2001]
TMRC	Tech Model Railroad Club [MIT]
TMRC	Transportation Modeling Research Center (TMRC {above} alter ego)
TNC	Threaded Neill Concelman (connector) [electronics] (see also BNC)
TNT	TriNitro Toluene
TOS	Transfer Orbit Stage [Space]
TP	from TP0 and TP4 (ISO/CCITT Transport Services; like TCP)
TPC	The Phone Company (from classic movie: _The President's Analyst_)
TSS	Tethered Satellite System [Space]
TSTO	Two Stage to Orbit [Space]
TTL	Transistor Transistor Logic
TTY	TeleTYpe
TV	TeleVision
TVA	Tennesee Valley Authority
TWA	Trans World Airlines
TWIMC	To Whom It May Concern
TWX	TeletypeWriter eXchange
u	(representing the greek mu) - micro
UA	United Artists
UAR	United Arab Republic
UART	Universal Asynchronous Receiver Transmitter
UBA	UniBus Adapter [DEC]
UBC	University of British Columbia
UCAR	University Corporation for Atmospheric Research
UCL	University College London
UFO	Unidentified Flying Object
UHF	Ultra High Frequency (300-3000MHz)
UK	United Kingdom
UL	Underwriters Laboratory
UN	United Nations
UNESCO	United Nations Educational, Scientific, & Cultural Organization
UNICEF	United Nations International Children's Emergency Fund (now UN Child. Fund)
UP	Union Pacific (railroad) [Corporate name]
UPI	United Press International [Corporate name]
UPS	Uninterruptible Power Supply
UPS	United Parcel Service [Corporate name]
US	United States (of America)
USA	Union of South Africa
USA	United States Army
USA	United States of America
USAF	United States Air Force
USAFA	United States Air Force Academy (in Colorado Springs)
USAN	University Satellite Network
USGS	United States Geologic Survey
USN	United States Navy
USO	United Service Organizations
USPS	United States Postal Service
USS	United States Ship
USSR	Union of Soviet Socialist Republics
UT	Universal Time
UTC	Coordinated Universal Time
UV	UltraViolet
VA	Veterans Administration
VAR	Value Added Remarketers
VAT	Value Added Tax
VAX	Virtual Address eXtended
VCO	Voltage Controlled Oscillator
VCR	VideoCassette Recorder
VD	Venereal Disease (see also STD)
VF	Video Frequency
VF	Voice Frequency
VFW	Veterans of Foreign Wars
VHF	Very High Frequency (30-300MHz)
VHS	Video Home System (VCR)
VIP	Very Important Person
VISTA	Volunteers In Service To America
VJ	Video Jockey
VLA	Very Large Array radio telescope in Arizona or New Mexico
VLF	Very Low Frequency (3-30KHz)
VLSI	Very Large Scale Integration
VM	Virtual Memory
VMOS	Vertical Metal Oxide Semiconductor (V-MOS) (see MOS)
VOA	Voice Of America
VRC	Vertical Redundancy Character
VSAT	Very Small Aperture Terminal
VTAM	Virtual Telecommunications Access Method [IBM]
VTOL	Vertical TakeOff and Landing
W	West
WA	Western Australia
WAC	Womens Air Corps
WAN	Wide Area Network
WATS	Wide Area Telephone Service
WG	Working Group
WORM	Write Once, Read Many time
WSI	Wafer Scale Integration
WSW	West-SouthWest
WU	Washington University
WU	Western Union
WV	West Virginia
WW	World War
XFER	Transfer
XL	eXtra Large
XMTR	transMiTteR (the X is for trans)
XNS	Xerox Network Services
XOR	eXclusive OR (logical function)
XPORT	Transport
XTAL	crysTAL (another version of x for crys, see XMTR)
YA...	Yet Another
YMCA	Young Mens Christian Association
YST	Yukon Standard Time
YT	Yukon Territory
YT	Yukon Time
YWCA	Young Womens Christian Association
ZIP	Zone Improvement Plan (post office code)
ZPG	Zero Population Growth