| Abbreviation | Definition |
|---|---|
| OAT | Overall Test |
| OB | Onboard |
| OB | Operational Base |
| OB | Optical Bench |
| OB | Outboard |
| OBC | On Board Camera |
| OBC | On Board Computer |
| OBC | Onboard Computer |
| OBCO | OnBoard CheckOut |
| OBCO | Onboard Checkout (Instrumentation) |
| OBCS | Onboard Checkout Subsystem |
| OBCS | OnBoard Checkout System |
| OBD | On Board Diagnostics |
| OBDH | On Board Data Handling |
| OBDI | On-Board Decoder Interface (NASA) |
| OBDU | On-Board Diagnostic Unit |
| OBE | Outboard Booster Engine |
| OBS | OBServe |
| OBS | Observe, Observer |
| OBS | Operational Bioinstrumentation System |