AS
- as – (i) Adult swim – (s) Assamese language (ISO 639-1 code) – Attosecond
- aS – (s) Attosiemens
- As – (s) Arsenic
- AS – (s) American Samoa (postal symbol; ISO 3166 digram) – Australia (FIPS 10-4 country code) – Assam / Asom (Indian state code)
- AS – (i) ActionScript
- A/S – (i) Anti-submarine
- A&S – (i) Armament & Standardisation
- ASA – (i) AcetylSalicylic Acid – American Standards Association – Army Security Agency – Atlantic Southeast Airlines
- ASAP – (a) As Soon As Possible
- ASARS – (a) Advanced Synthetic Aperture Radar System – Airborne Search and Rescue System
- ASB – (i) Associated Student Body – Alternative Service Book (Church of England)
- asbl – (i) association sans but lucratif (French "Non-profit organisation")
- ASBO – (a) Anti-Social Behaviour Order
- ASCAP – (a) American Society of Composers, Authors, and Publishers
- ASCC – (i) Army Service Component Commander – Automatic Sequence Controlled Calculator – Air Standardization Coordinating Committee
- ASCIET – (i) All Services Combat Identification Evaluation Team
- ASCII – (a) American Standard Code for Information Interchange
- ASC+T – (i) Anti Slip Control + Traction
- ASD – (i) (U.S.) Assistant Secretary of Defense – autism spectrum disorder
- ASD(C3I) – (i) (U.S.) (Command, Control, Communications, & Intelligence)
- ASD(FMP) – (i) (U.S.) Assistant Secretary of Defense (Force Management Policy)
- ASD(HA) – (i) (U.S.) Assistant Secretary of Defense (Health Affairs)
- ASD(ISA) – (i) (U.S.) Assistant Secretary of Defense (International Security Affairs)
- ASD(ISP) – (i) (U.S.) Assistant Secretary of Defense (International Security Policy)
- ASD(LA) – (i) (U.S.) Assistant Secretary of Defense (Legislative Affairs)
- ASD(PA) – (i) (U.S.) Assistant Secretary of Defense (Public Affairs)
- ASD(RA) – (i) (U.S.) Assistant Secretary of Defense (Reserve Affairs)
- ASD(SO&HA) – (i) (U.S.) Assistant Secretary of Defense (Special Operations & Humanitarian Assistance)
- ASD(SO/LIC) – (i) (U.S.) (Special Operations & Low-Intensity Conflict)
- ASD(S&R) – (i) (U.S.) Assistant Secretary of Defense (Strategy & Requirements)
- ASD(S&TR) – (i) (U.S.) Assistant Secretary of Defense (Strategy & Threat Reduction)
- ASDIC – (a) Allied Submarine Detection Investigation Committee (Sonar)
- ASEAN – (a) Association of South East Asian Nations
- ASFAR – (a) Americans for a Society Free of Age Restrictions
- ASG – (i) Area Support Group
- ASIC – (a) Australian Securities and Investments Commission – (a) Aviation Security Identification Card
- ASICS – (a) Anima sana in corpore sano (Latin, "A sound mind in a sound body") (athletic shoe manufacturer)
- ASIO – (a) Australian Security Intelligence Organisation – (a) Audio stream input output
- ASIP – (i) Advanced System Improvement Program – Army Stationing and Installation Plan – Application-specific instruction-set processor
- ASL – (i) Above Sea Level – American Sign Language (also known as Ameslan) – "Age, Sex, Location?" (Internet slang)
- asm – (s) Assamese language (ISO 639-2 code)
- ASM – (i) Air-to-Surface Missile – (s) American Samoa (ISO 3166 trigram) – (i) American Society for Metals – (i) American Society for Microbiology
- ASMB – (i) American Society for Matrix Biology – Adult Swim Message Board
- ASME – (i) American Society of Mechanical Engineers – American Society of Magazine Editors
- ASMP – (i) Air-Sol Moyenne Portée missile (French "Medium-range air to surface") – (p) Asymmetric multiprocessing
- ASN – (i) Associate of Science in Nursing
- ASOC – (a/i) Air Sovereignty Operations Centre – Air Support Operations Centre – Airport Security and Operations Centre – Antarctic and Southern Ocean Coalition – Atlanta Symphony Orchestra Chorus – Australian Standard Offence Classification
- ASP – (i) Active Server Pages – American Society of Primatologists – Ammunition Supply Point – Application Service Provider (cf internet service provider) – Astronomical Society of the Pacific – Association of Surfing Professionals
- ASPI – (i) Australian Strategic Policy Institute
- ASR – (i) Alkali-silica reaction – Anti Slip Regulation
- ASRAAM – (a) Advanced Short-Range Air-to-Air Missile
- ASSC – (i) Association for the Scientific Study of Consciousness
- Ass Paym – Assistant Paymaster
- AST – (i) Atlantic Standard Time (UTC-4 hours)
- ASTIA – (a) Armed Services Technical Information Agency
- ASTM – (i) American Society for Testing and Materials
- ASTREA – (a) Aerial Support To Regional Enforcement Agencies (sheriff's air support unit)
- ASUW – (p) AntiSUrface Warfare
- ASVAB - Armed Services Vocational Aptitude Battery(taken by juniors in high school in the USA)
- ASVEL – (a) Association Sportive Villeurbanne Éveil Lyonnais (Association Sportive is French for "Sporting Association"; the club was founded through the merger of AS Villeurbanne and Éveil Lyonnais)
- ASW – (i) AntiSubmarine Warfare
- ASWORG – (i) (U.S.) AntiSubmarine Warfare Operations Research Group
- ASX – (p) Advanced Stream Redirector – Australian Securities Exchange
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