| Abbreviation | Definition |
|---|---|
| MMCU | Maryville Municipal Credit Union |
| MMCU | Metro Medical Credit Union |
| MMCU | Moline Municipal Credit Union |
| MMCU | Money Matters Credit Union |
| MMMU | Motivators and Master Motivators Union |
| MMPU | Musical Mutual Protective Union |
| MMU | Micro Monde Union |
| MMU | Mount Mansfield Union |
| MNA | Massachusetts Nurses Association |
| MNA | Michigan Nurses Association |
| MNA | Minnesota Nurses Association |
| MORE | Marketing, Organizing, Recruitment, and Empowerment |
| MOU | Minnesota Ornithologists Union |
| MOU | Minnesota Ornithologists' Union |
| MPU | Medical Practitioners' Union |
| MPU | Mediterranean Phytopathological Union |
| MRFU | Malta Rugby Federation Union |
| MRFU | Malta Rugby Football Union |
| MRFU | Marlborough Rugby Football Union |
| MRFU | Midwest Rugby Football Union |