| Ammonia-Oxidizing Archaea | Academic & Science |
| ASCA Online Arxiv | Academic & Science |
| Alpha Omega Alpha (ΑΩΑ) | Academic & Science |
| Argentine Odontological Association | Academic & Science |
| Asociación Odontológica Argentina | Academic & Science |
| Australian Orthopaedic Association | Academic & Science |
| Andrews Osborne Academy | Academic & Science |
| Academic Opportunities in America | Academic & Science |
| Auditing Oversight Authority (slovak Republic) | Accounts and Finance |
| Aroa | Airport Code |
| Airport Operators Association | Associations & Organizations |
| American Ostrich Association | Business |
| American Optometric Association | Business |
| Asian Ombudsman Association | Business |
| Arizona Orthopaedic Associates | Business |
| Association of Otolaryngology Administrators | Business |
| Atlanta Ophthalmology Associates | Business |
| Advanced Office Automation | Business |
| Advance Order Authorisation | Business |
| Articles Of Association | Business |
| Affordable Online Advertising | Business |
| Authorised OECD Approach | Business |
| Anhydrous Oripavine Alkaloid | Chemistry |
| Alaska Optometric Association | Community |
| Auxiliary Organizations Association | Community |
| Apartment Owners Association | Community |
| Alpaca Owners Association | Community |
| American Outlaws Association | Community |
| Alliance of Overclocking Arts | Computer Hardware |
| All Of the Above | Computing |
| Angolan Kwanza | Country Currency |
| Absolutely Outrageous Acronym | General |
| Assalam-O-Alaikum | General |
| Ace of Angels | General |
| Active Older Adult | General |
| All Over Ayrshire | General |
| Active Older Adults | General |
| Avenue of the Americas | General |
| Aircraft Operations Area | General |
| Activity On Arrow | General |
| Appalachia Outdoor Adventures | General |
| Ace of Angles | General |
| Age of Apocolypse | General |
| Activity On Arc | General |
| ASCA online archive | General |
| Arizona Outback Adventures | General |
| Air Office Administration | General |
| Accuracy of Acceptance | General |
| Amphibious Operations Area | General |
| Analysis of Actions | General |
| Adidas Only Addiction | General |
| Adult Onset Aviator | General |
| Amphibious Operating Area | General |
| Airport Operations Area | General |
| Agreement on Agriculture | Governmental |
| Administration On Aging | Governmental |
| Air Operations Area | Governmental |
| Any One Accident | Governmental |
| Angle Of Attack | Governmental |
| Abort Once Around | Governmental |
| American Osteopathic Association | Healthcare |
| Announcement On Arrival | Internet |
| Aimms Outer Approximation Algorithm | Maths |
| Age of Acquisition | Medical |
| Alive On Arrival | Medical |
| American Orthopaedic Association | Medical |
| Ataxia with oculomotor apraxia | Medical |
| Analysis of Alternatives | Military and Defence |
| Amphibious Objective Area | Military and Defence |
| Abbreviated Operational Assessment | Military and Defence |
| Angle of Arrival | Military and Defence |
| Add- On Armor | Military and Defence |
| Attack On Acquisition | Military and Defence |
| Kwanza | Regional |
| Annual Operating Agreement | Space Science |
| Age of Apocalypse | Sports |
| Alberta Orienteering Association | Sports |
| Art of Athletics | Sports |
| American Overseas Airlines | Transport & Travel |
