| Abbreviation | Definition |
|---|---|
| MSBA | Michigan Sport Buggy Association |
| MSCP | Model Show & Contest Pictorial |
| MSCT | Multiple Sound Combination Test |
| MSCW | Mazda Sportscar Club of Washington |
| MSFA | Memphis Science Fiction Association |
| MSG | Mobile Suit Gundam |
| MSIC | Mustard Seeds Investment Club |
| MSN | Mississauga Snake Network |
| MSRA | Manitoba Street Rod Association |
| MSRA | Minnesota Street Rod Association |
| MSS | Mario Super Sluggers |
| MSSS | Mike's Scale Speed Shop |
| MSTA | Montata State TrapShooting Association |
| MSTA | Motorcycle Sport Touring Association |
| MTCE | Motorcycle Touring Club Europe |
| MTF | Motorcycle Tourer's Forum |
| MTFF | Man-Tended Free Flyer |
| MTFF | Middle Tennessee Fly Fishers |
| MTYGF | Montana - Yellowstone Geneaology Forum |
| MUFON | Mutual Unidentified Flying Object Network |