| Abbreviation | Definition |
|---|---|
| MUSA | Methodist Union of Social Agencies |
| MUSO | Memorial Union Student Organization |
| MUST | Management and Unions Serving Together |
| MUT | Malta Union of Teachers |
| MUTO | Michigan Union Ticket Office |
| MUZ | Mineworkers Union of Zambia |
| MVU | Missisquoi Valley Union |
| MWASA | Media Workers Association of South Africa |
| MWCU | Manly Warringah Credit Union |
| MWCU | Minnequa Works Credit Union |
| MWU | Maccabi World Union |
| MWU | Mazda Workers Union |
| MWU | Millennium Workers Union |
| MWU | Mine Workers Union |
| MWU | Miscellaneous Workers Union |
| NACODS | National Association of Colliery Overmen, Deputies and Shotfirers |
| NACTWUSA | National Clothing and Textile Workers Union of South Africa |
| NACU | National Alliance of Communications Unions |
| NAFU | North American Football Union |
| NAKISS | National Association of Akwa Ibom State Students |