| Abbreviation | Definition |
|---|---|
| SIMUTA | Simulation for Multiple Unit Training Assemblies |
| SIMWIN | Simulated Workstation Input |
| SIMWOUT | Simulated Workstation Output |
| SIN | Strength In Numbers |
| SINCGARS | Single Channel Ground and Air(borne) Radio System |
| SINCGARS | Single-Channel Ground and Airborne Radio System |
| SINCGARS-SIP | Single Channel Ground and Air(borne) Radio System - System Improvement Program |
| SINE | Short Interspersed Nuclear Element |
| SINGARS | Single Channel Ground Air Radio System |
| SINS | Ship's Inertial Navigation System |
| SIO | Senior Intelligence Officer |
| SIO | Special Information Operations |
| SIO | Standard Installation Organization |
| SIOP | Single Integrated Operational Plan |
| SIOP-ESI | Single Integrated Operational Plan-Extremely Sensitive Information |
| SIP | Support Incident Pack |
| SIP | System Enhancement Program |
| SIP | System Implementation Plan |
| SIP | System Improvement Program |
| SIPE | Soldier Integrated Protective Ensemble |