| Acronym | Definition |
|---|
| PIRA | Provisional Irish Republican Army |
| PIRA | Physics Instructional Resource Association |
| PIRA | Petroleum Industry Research Associates (PIRA Energy Group) |
| PIRA | Precision Impact Range Area |
| PIRA | PADI International Resort Association |
| PIRA | Paper Industry Research Association |
| PIRA | Printing Industries Research Association |
| PIRA | Personnel and Industrial Relations Association (est. 1945; Los Angeles, CA) |
| PIRA | Parachute Infantry Regiment Association (UK) |
| PIRA | Philippine Insurance Rating Association |
| PIRA | Paper, Printing and Packaging Industries Research |
| PIRA | Pre-Inactivation Restricted Availability (US Navy) |
| PIRA | Plastics Industry Research Association (UK) |