| Abbreviation | Definition |
|---|---|
| OCF | Old Cardinal Fan |
| OCIR | Orange County International Raceway |
| OCRR | Orange County Rebel Riders |
| OCRR | Orange County Rookie Rider |
| OCS | On The Course Side |
| OCS | Opposition Caught Stealing |
| OCSA | Orange County Sportsmen's Association |
| OCSC | Orange Council of Ski Clubs |
| OCSG | Open Canoes Sailing Group |
| OCSN | Official College Sports Network |
| OCT | Oklahoma City Thunder |
| OCTR | Orange County Trail Runners |
| OD | Olympic Development |
| ODAC | Old Dominion Aquatic Club |
| ODBA | Outboard Drag Boat Association |
| ODC | Opening Day Committee |
| ODC | Outdoor Discovery Craft |
| ODD | Oddity Death Drop |
| ODER | One Day Endurance Run |
| ODM | Ocean Drive Marathon |