| Abbreviation | Definition |
|---|---|
| R&I | Receipts and Issues |
| R&O | Repair and Overhaul |
| R&R | Recruitment and Retention |
| R&R | Refit and Repair |
| R&R | Rest and Recreation |
| R&R | Rest and Recuperation |
| R&S | Reconnaissance and Surveillance |
| R.440 | Crotale Missile |
| R.550 | Magic Misile |
| R.S.M. | Regimental Sergeant Major |
| R/EW | Radar/ Electronic Warfare |
| R/O | Receive Only |
| R2 | Reporting Responsibility |
| R2C | Ready and Resilient Campaign |
| R2C | Route Reconnaissance and Clearance |
| R2P2 | Rapid Response Planning Process |
| R2T2 | Rapid Response Topographic Teams |
| R3P | Rearm, Refuel, Resupply point |
| RA | Military Serial Number prefix for non-drafted Volunteer |
| RA | Rally America |