| Abbreviation | Definition |
|---|---|
| RTX | Real Time Executive |
| RU | Rack Unit |
| RU | Ready Units |
| RU | Reinforced Unit |
| RU | Release Unit |
| RU | Replaceable Unit |
| RU | Request Unit |
| RU | Rescue Unit |
| RU | Reserve Unit |
| RUF | Rapid Ultrasonic Firing |
| RUF | Rules For The Use of Force |
| RUIC | Reserve Unit Identification Number |
| RUM | Resource and Unit Monitoring |
| RUMINT | RUMor INTelligence |
| RUMINT | RUMour INTelligence |
| RUP | Reduction in Unit Publications |
| RUR | Repair, Update, And Refurbish |
| RUR | Royal Ulster Rifles |
| RUR-4 | suRface to Underwater Rocket model 4 (Weapon Alpha) |
| RUR-4 | Weapon Alpha ( Anti-submarine Rocket Launcher) |