| Abbreviation | Definition |
|---|---|
| MSC | Military Space Cruiser |
| MSR | Mulder Scully Romance |
| MST | Mystical Space Typhoon |
| MST3k | Mystery Science Theater 3000 |
| MSTT | Motion Sickness of Time Travel |
| MT | Mars Trojan |
| MT | Minas Tirith |
| MT | Mirai Trunks |
| MTF | Mobile Task Force |
| MTFF | Miaka and Tamahome Fan Fiction |
| MTFN | MegaTokyo Fan Network |
| MTR | Mortality Time Recognition |
| MUFO | Martian Unidentified Flying Object |
| MUTT | Multi-Universal Temporal Transporter |
| MWEC | Muggle-Worthy Excuse Committee |
| NADA | North American Dark Army |
| NATHAN | Networked Android Trained For Hazardous Assassination And Nullification |
| NAVR | North American Vampire Registry |
| NAW | Neo Azeroth World |
| NCSF | Nederlands Contactcentrum voor Science Fiction |