| Abbreviation | Definition |
|---|---|
| OW | Overall Width |
| OWTX | Oneida & Western Transportation |
| OWV | Over Width Vehicle |
| OXS | Oxygen Sensor |
| OYR | Off Your Road |
| OYR | Old York Road |
| OYR | One Year Recall |
| OYTS | Own Your Train Scheme |
| P | Passenger |
| P | Planning |
| P | Porsche |
| P2P | Park to Park (Trail) |
| PA | Port Authority |
| PABT | Port Authority Bus Terminal |
| PAC | Pacific Region |
| PAC | Port Authorization Code |
| PACE | Pilot Aircraft Courtesy Evaluation |
| PACS | Passenger-Aircraft Co-ordination System |
| PACTS | Portland Area Comprehensive Transportation System |
| PAD | Petroleum Administration for Defense |