| Abbreviation | Definition |
|---|---|
| PIR | Para Infantry Regiment |
| PIR | Pass In Review |
| PIR | Passive Infra Red |
| PIR | Post-Implementation Review |
| PIR | Primary Image Record |
| PIR | Priority Information Requirement |
| PIR | Priority Intelligence Requirement |
| PIR | Priority Intelligence Requirements |
| PIR | Problem Identification Report |
| PIRAZ | Positive Identification and Radar Advisory Zone |
| PIRC | Program to Improve Reserve Components |
| PIROMA | Pulled It Right Out Of My Ass |
| PIRT | Purposeful Interference Response Team |
| PISO | Privacy and Information Security Officers |
| PIT | Photo Interpretation Tool |
| PITS | Platform Integrated Transmitter System |
| PIU | Programmable Interface Unit |
| PIVADS | Product Improved Vulcan Air Defense System |
| PIW | Person In Water |
| PIXEL | Picture Element |