S
- SA – Seaman Apprentice (USCG/USN E-2)
- SAS – Special Air Service (British special forces)
- SBS – Special Boat Service (British special forces)
- SAAS – Standard Army Ammunition System (U.S. Army)
- SAM – Surface-to-air Missile
- SARSS – Standard Army Retail Supply System (U.S. Army)
- SCPO – Senior Chief Petty Officer (USCG/USN E-8)
- SEAL – Sea, Air and Land (US Navy SEALs)
- SERE – Survival, Evasion, Resistance and Escape
- SFC – Sergeant First Class (U.S. Army E7)
- SGM – Sergeant Major (U.S. Army E9 – Sometimes referred to as Staff Sergeant Major)
- SGT – Sergeant (U.S. Army E5)(U.S. Marines uses Sgt)
- SITREP – Situation Report
- SLAM – Standoff Land Attack Missile
- SMA – Sergeant Major of the Army (U.S. Army E9 – Senior Enlisted Member)
- SMEAC Situation Mission Execution Admin/logistics Command/signal (US Marine Corps basic knowledge)
- SMSgt – Senior Master Sergeant (USAF E-8)
- SN – Seaman (USCG/USN E-3)
- SNAFU – Situation Normal: All Fucked Up
- SOCOM – United States Special Operations Command
- SOFA – Status of Forces Agreement
- SOP – Standard Operating Procedures
- SOS – Shit On a Shingle, or creamed chipped beef on toast.
- SPC – Specialist (U.S. Army E-4)
- SR – Seaman Recruit (USCG/USN E-1)
- SrA – Senior Airman (USAF E-4)
- SRR – Special Reconnaissance Regiment (British special Forces)
- SSDD – Same Shit Different Day
- SSDDBS – Same Shit Different Day Bigger Shovel
- SSG – Staff Sergeant (US Army E-6)
- SSgt – Staff Sergeant (US Air Force E-5)(U.S. Marines E-6)
- SOL – Shit Out of Luck (US Army)
- SOLJWF – Shit Out of Luck and Jolly Well Fucked (U.S. Marines)
- SUSFU – Situation Unchanged, Still Fucked Up
- SWAG – Scientific Wild Ass Guess
Read more about this topic: List Of U.S. Government And Military Acronyms