| Abbreviation | Definition |
|---|---|
| ORF | Old Retired Fart |
| ORL | Oto- RhinoLaryngologist |
| ORL | Oto-RhinoLaryngologist |
| ORM | Occupational Risk Management |
| ORO | Over Raise Only |
| OS | Ordinary Seaman |
| OS | Other Singer |
| OS | Out Sized |
| OSA | Office Support Assistant |
| OSC | On Scene Coordinator |
| OSCAR | Occupational Skills Competition And Review |
| OSCI | One Stroke Certified Instructor |
| OSE | Office of the State Engineer |
| OSJ | Order Of St John |
| OT | Occupational Therapist |
| OT | Occupational Transfer |
| OT | Old Timer |
| OT | Opportunity Transfer |
| OTA | Occupational Therapy Assistant |
| OTE | On Target Earnings |