| Abbreviation | Definition |
|---|---|
| SIE | Self Initiated Elimination |
| SIGN | Scottish Intercollegiate Guidelines Network |
| SIMA | Super International Mega Ace |
| SIMS | Sports Injury Monitoring System |
| SINC | Sports Industry Networking and Career |
| SINI | Sports Institute Northern Ireland |
| SIP | Stay In Play |
| SIPT | Sharps Injury Prevention Team |
| SIR | Scottish Ice Rink |
| SIR | Sport Injected Race |
| SIRA | Southern Intercollegiate Rowing Association |
| SIRC | Sport Information Resource Centre |
| SIRU | Southern Inland Rugby Union |
| SIT | Skater In Training |
| SITS | Soccer In The Streets |
| SJ | Season Joined |
| SJ | Side Judge |
| SJ | Super Jump |
| SJ | Super Jumping |
| SJCCP | St. John's College Croquet Party |