| 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) |