AAC
- AAC Honey Badger
- Adenine nucleotide translocator
- Adult Association of Canada
- Advanced Aircraft
- Advanced Armament Corporation
- Advanced Audio Coding
- Affirming Anglican Catholicism
- Air arc cutting
- Airborne aircraft carrier
- Alameda Arts Council
- Alaskan Air Command
- American Aeronautical Corporation
- American Airlines Center
- American Alpine Club
- American Anglican Council
- American Aviation
- American Conference (NCAA)
- Amphibian Airplanes of Canada
- Anesthesiologist assistant
- Anne Arundel County, Maryland
- Anthony Abell College
- Anti-Aircraft Warfare
- Antimicrobial Agents and Chemotherapy
- Appalachian Athletic Conference
- Ari language (New Guinea)
- Armenian Apostolic Church
- Army Air Corps (United Kingdom)
- Army Apprentices College
- Art Academy of Cincinnati
- Asia-Pacific Amateur Championship
- Association of Alabama Camps
- Association of American Colleges
- Associação Académica de Coimbra
- Associação Académica de Coimbra – O.A.F.
- Associação Académica de Coimbra – basketball
- Associação Académica de Coimbra – volleyball
- Atlanta Athletic Club
- Audax Alpine Classic
- Augmentative and alternative communication
- Australian Agricultural Company
- Australian Air Corps
- Australian Aluminium Council
- Australian Army Cadets
- Auto Avio Costruzioni 815
- Autoclaved aerated concrete
- Awami Action Committee
- Civil Aviation Authority (El Salvador)
- Civil Aviation Authority (Panama)
- Coimbra Academic Association
- El Arish International Airport
- Photochrom
- Pseudomembranous colitis
- United States Army Acquisition Corps
- United States Army Air Corps
- Western North Carolina Athletic Conference