| Acronym | Meaning |
| RUB | Russian Ruble (ISO 4217 Currency Code) |
| RUC | Royal Ulster Constabulary |
| RUN | Kirundi Language (ISO 639-2 Code) |
| RUS | Russia (ISO 3166 Trigram) |
| RUS | Russian Language (ISO 639-2 Code) |
| RUSI | Royal United Services Institute For Defence Studies |
| RV | Reconnaissance Vehicle - Recreational Vehicle - Re-entry Vehicle |
| RW | Kinyarwanda Language (ISO 639-1 Code) |
| RW | Rwanda (ISO 3166 And FIPS 10-4 Country Code Digram) |
| RWA | Rwanda (ISO 3166 Trigram) |
| RWADA | Resident Weighted Average Daily Attendance (New York State Term Used In Public Education To Indicate The Size Of A School District |
| RWF | Rwandan Franc (ISO 4217 Currency Code) |
| RWR | Radar Warning Receiver |
| RWS | Remote Weapon Station |
| RX | Medical Prescription (possibly From Latin Recipere |
| RX | Receive |
| S | Siemens - South - Sulfur |
| S&TCD | CERDEC Space And Terrestrial Communications Directorate |
| S/SSM | Surface-to-Subsurface Missile |
| SA | Sand (METAR Code) - Saudi Arabia (ISO 3166 And FIPS 10-4 Country Code Digram) -sine Anno (Latin |
| SA | Sanskrit Language (ISO 639-1 Code) |
| SAAB | Svenska Aeroplan AB (Swedish Aircraft And Automobile Manufacturer) |
| SAAFR | Standard Use Army Aircraft Flight Route (safer) |
| SAARC | South Asian Association For Regional Cooperation |
| SABENA | Soci?t? Anonyme Belge D'exploitation De La Navigation A?rienne (French For Belgian Company For Exploiting Aerial Navigation |
| SABR | Society For American Baseball Research |
| SAC | Standards Activity Committee (of SISO) - U.S. Strategic Air Command (1946-1992) |
| SACEUR | Supreme Allied Commander EURope |
| SACLANT | Supreme Allied Commander AtLANTic |
| SACLOS | Semi-Automatic Command To Line Of Sight |
| SAD | Seasonal Affective Disorder - Situational Awareness Display |
| SADD | Students Against Drunk Driving (national School Related Group) |
| SADL | Situation Awareness Data Link (saddle) - Structural Architecture Description Language |
| SAE | Society Of Automotive Engineers - Stamped Addressed Envelope |
| SAFER | Steel And Foam Energy Reduction |
| SAFICT | Software Agents As Facilitators Of Interoperability In Collective Training |
| SAG | Sango Language (ISO 639-2 Code) |
| SAGAT | Situation Awareness Global Assessment Technique |
| SAGE | Semi-Automatic Ground Environment (simulation) |
| SAHB | Sensational Alex Harvey Band |
| SAIC | Science Applications International Corporation |
| SALT | Southern African Large Telescope - Strategic Arms Limitation Talks |
| SALT | Save A Life Today - Save A Life Today (SALT) Alert - Emergency Contact System |
| SAM | Sequential-Access Memory - Sociedad Aeron˙utica De Medelln - Surface-to-Air Missile |
| SAML | Security Assertion Markup Language (sam-ell) |
| SAN | Sanskrit Language (ISO 639-2 Code) |
| SAR | Saudi Riyal (ISO 4217 Currency Code) -Search And Rescue - Special Administrative Region - Synthetic Aperture Radar |
| SARA | Southeastern Association For Research In Astronomy - Scientific Atlanta Resident Application - Scottish Amateur Rowing Association - Southern African Railway Association - State Administration For Religious Affairs |
| SARP | Search And Rescue Processor |
| SARR | Search And Rescue Repeater |