| Abbreviation | Definition |
|---|---|
| MSSA | Minnesota State Student Association |
| MSSA | Missouri Sport Shooting Association |
| MSSA | Montreal Student Space Associations |
| MSSA | Mountain States Stockdog Association |
| MSSDA | Midsouth Stock Dog Association |
| MSTA | Maine Science Teachers Association |
| MSTA | McLean Swimming and Tennis Association |
| MSTA | Mid South Trails Association |
| MSTA | Mississippi Science Teachers Association |
| MSTA | Missouri State Teacher Association |
| MSTA | Montana Science Teachers Association |
| MSVA | Madison Street Veterans Association |
| MSVW | Main Street Van Wert (development association) |
| MSZS | Miejski Szkolny Zwiazek Sportowy (Polish: Urban School Sports Association) |
| MSZV | Mitteldeutscher Schweinezuchtverband (German: Central German Pig Breeding Association) |
| MTA | Maitland Trail Association |
| MTA | Market Technicians Association |
| MTA | Michigan Townships Association |
| MTAC | Motor Transport Association of Connecticut |
| MTAC | Motor Transportation Association of Connecticut |