| Abbreviation | Definition |
|---|---|
| OMO | Occupational Medicine Office |
| OMP | Other Major Parks |
| OMPQ | Office of Manufacturing and Product Quality |
| ONC | Office of the National Coordinator |
| ONCHI | Office of the National Coordinator for Health Information Technology |
| ONDCP | Office Of National Drug Control Policy |
| ONEST | Overseas Nuclear Emergency Search Team |
| ONF | Olympic National Forest |
| ONHIR | Office of Navajo and Hopi Indian Relocation |
| ONOL | Off-Network Overseas Location |
| ONP | Office of National Preparedness |
| ONP | Office of Naval Procurement |
| ONP | Olympic National Park |
| ONPI | Office of News and Public Information |
| OOA | Out Of Air |
| OODA | Observation, Orientation, Decision, and Action |
| OOEA | Office of Outreach and Exporter Assistance |
| OOG | Out Of Government |
| OOM | Office of Occupational Medicine |
| OOMAB | Office Of Management And Budget (US government; usually seen as OMB) |