| Abbreviation | Definition |
|---|---|
| LYU | Lao Youth Union |
| M | married |
| MAAU | Malaysia Amateur Athletics Union |
| MACU | Members Advantage Credit Union |
| MAMU | Mahanagar Asangathit Mazdoor Union |
| MANU | Mozambican African National Union |
| MASU | Maxwell African Scholars Union |
| MATUSA | Municipal and Allied Trade Union of South Africa |
| MBU | Mind Body Union |
| MCAU | Missouri College Athletic Union |
| MCCU | Members Cooperative Credit Union |
| MCTU | Malawi Congress of Trade Unions |
| MCU | Meadows Credit Union |
| MCU | Millbury Credit Union |
| MCU | Missouri Credit Union |
| MCU | Municipal Credit Union |
| MDU | Midwest Drift Union |
| MDUM | Medical Doctors Union of Malawi |
| MDWU | Madison Downtown Workers Union |
| MDWU | Maritime and Dockworkers Union |