PIRR
| Acronym | Definition |
|---|---|
| PIRR | Project Internal Rate of Return |
| PIRR | Participating Individual Ready Reserve (Air Force Reserve) |
| PIRR | Pi times Radius Squared |
| PIRR | Payload Increment Readiness Review (space vehicles) |
| PIRR | Preliminary Investigation Request Response (Raytheon) |
| PIRR | Prepositioned War Reserve Interrogation and Readiness Reporting |
| PIRR | Participating Individual Ready Reservist (US DoD) |
| PIRR | Peripheral Inflammatory Root Resorption (dentistry) |
| PIRR | Polski Instytut Rozwoju Rynku (Warsaw, Poland) |