| Abbreviation | Definition |
|---|---|
| NMDU | Newspaper and Mail Deliverers Union |
| NMHU | National Mail Handlers Union |
| NMPA | National Master Processing Agreement |
| NMTU | New Model Trade Union |
| NMTU | Next Media Trade Union |
| NMU | National Maritime Union of America |
| NMU | National Miners Union |
| NMUA | National Maritime Union of America |
| NOC | National Organizing Committee |
| NOLC | Niagara-Orleans Labor Council |
| NOLC | Northwest Oregon Labor Council |
| NORD | National Office, Regions, and Districts |
| NORKA | Non-resident Keralites Affairs |
| NORKA | Non-resident Keralites' Affairs |
| NOSU | Northholm Old Students Union |
| NOU | Nebraska Ornithologists' Union |
| NPCU | National Police Credit Union |
| NPSU | Non-Partisan Solidarity Union |
| NPU | National Provincial and Union |
| NPWU | Natioinal Postal Workers Union |