| Abbreviation | Definition |
|---|---|
| AMTRA | Australian Motorcycle Trail Riders Association |
| ANC | Arts aNd Crafts |
| ANCC | Association of Northern Car Clubs |
| ANMD | Alliance Navy Marine Division |
| ANUS | American Nihilistic Underground Society |
| ANWB | Algemene Nederlandse Wielrijders Bond |
| AO | Argentum Online |
| AOF | Angry Old Farts (On-line Family Gaming Community) |
| APCA | Association of Philatelic Chroniclers of Argentina |
| APHC | Appaloosa Horse Club |
| APIC | American Political Items Collectors |
| APO | Amateur Philatelists Organization |
| APOC | Atlanta Probe Owners Club |
| APS | American Philatelic Society |
| AQ | Adventure Quest |
| AQHA | American Quarter Horse Association |
| AQS | American Quilter's Society |
| AQSG | American Quilt Study Group |
| ARC | Air Rifle Club |
| AREM | All Random/Easy Mode (game setting) |