| Abbreviation | Definition |
|---|---|
| MHSA | Maryland Horse Show Association |
| MHSA | Maryland Horse Shows Association |
| MHSA | Missouri Horse Shows Association |
| MHSAA | Metropolitan High School Activities Association |
| MHSAA | Michigan High School Athletic Association |
| MHSAA | Milton Hershey School Alumni Association |
| MHSAA | Mississippi High School Activities Association |
| MHUA | Middlesex Hockey Umpires Association |
| MHWA | Maine Historical Wargamers Association |
| MHWA | Mental Health and Wellness Association |
| MHWA | Mental Health Wellness Association |
| MIAA | Maryland Interscholastic Athletic Association |
| MIAA | Michigan Intercollegiate Athletics Association |
| MIAA | Mid-America Intercollegiate Athletics Association |
| MIADA | Massachusetts Independent Automobile Dealers Association |
| MIADA | Missouri Independent Auto Dealers Association |
| MIAF | Maunatul Islam Association of Fiji |
| MIAO | Master Insulators Association of Ontario |
| MICA | Marco Island Civic Association |
| MICA | Minnesota Inter County Association |