| Abbreviation | Definition |
|---|---|
| MDWU | Montpelier Downtown Workers Union |
| MESHAWU | Municipality, Education, State, Health And Allied Workers Union |
| MEU | Model European Union |
| MEUC | Model European Union Creta |
| MEUS | Model European Union Strasbourg |
| MEWUSA | Metal and Electrical Workers Union of South Africa |
| MFOW | Pacific Coast Marine Firemen, Oilers, Watertenders, and Wipers Association |
| MFSU | Medical Faculty Students Union |
| MFU | Maritime Fishermen's Union |
| MFU | Minnesota Farmers Union |
| MFU | Montana Farmers Union |
| MGCU | Malta Government Clerical Union |
| MGU | Mpumalanga Golf Union |
| MHCU | Members Heritage Credit Union |
| MHCU | Memorial Health Credit Union |
| MICU | Montreal Island Citizens Union |
| MIOU | Mean Intersection Over Union |
| MIOU | Mean of Intersection Over Union |
| MIP | Membership Identification Program |
| MKU | Mahila Kisan Union |