| Abbreviation | Definition |
|---|---|
| OB | Obese |
| OB | OBstetrics |
| OBG | Journal of Obstetrics and Gynecology |
| OBJ | OBJect |
| OBJ | Objective |
| OBL | OBLique |
| OBL | Overdose Brings Life |
| OBP | Ova, Blood, and Parasites |
| OBS | Observation |
| OBS | OBServer |
| OBS | OBStetrics |
| OBS | Organic Brain Syndrome |
| OC | Obsessive Compulsive |
| OC | Oleoresin Capsicum (pepper spray for self-defense) |
| OC | On Call |
| OC | Oral Contraceptive |
| OCB | Obsessive Compulsive Behavior |
| OCC | Occasionally |
| OCC | Occiput |
| OCC | Occupation |