| Abbreviation | Definition |
|---|---|
| OA | Offer Accepted |
| OA | Operations Assistant |
| OAP | Old Age Pension |
| OAP | Old Age Premium |
| OASIS | Online Applicant Status and Information System |
| OB | Obstetrician |
| OBAT | Oil Burner Activation Technician |
| OBG | Obstetrics and gynecology |
| OCC | Occupational Character Class |
| OCD | Oriental Circus Dancer |
| OCG | Occupational Classifications Guide |
| OCI | On Campus Interviewing |
| OCJ | Ontario Court Judge |
| OCP | On a Career Path |
| OCP | Oracle Certified Professional |
| OCPJP | Oracle Certified Professional Java Programmer |
| OCS | Orthopaedic Certified Specialist |
| OD | Operating Dispatcher |
| ODB | Optional Dental Benefit |
| ODD | Official Designated Driver |