| Abbreviation | Definition |
|---|---|
| OAP | Old Age Pensioners |
| OAR | Chairman of The Joint Chiefs of Staff Operation Plans Assessment Report |
| OAR | Observe And Report |
| OAR | Of A Revolution |
| OAR | Operation Air Raid |
| OAS | Offensive Air Support |
| OAS | On Active Service |
| OAS | Operations Automation System |
| OAS | Organization of American States |
| OASD | Office of the Assistant Secretary of Defense |
| OASD(PA) | Office of The Assistant Secretary of Defense (Public Affairs) |
| OASD(RA) | Office of the Assistant Secretary of Defense (Reserve Affairs) |
| OASIS | Online Aerospace Supplier Information System |
| OASIS | Optimized Action Sequence Interpreter System |
| OASUW | Objective Anti-Surface Warfare |
| OASYS | Obstacle Avoidance System |
| OATS | Over Armor Technology Synthesis |
| OAV | Old Army Veterans |
| OAY | Outstanding Airman of the Year |
| OB | Operating Base |