| Abbreviation | Definition |
|---|---|
| MMIO | Memory-Mapped Input/Output |
| MO | Magneto-Optic |
| MPDA | Maine Professional Drivers |
| MRDL | Minor Restricted Drivers License |
| MSAS | Multiple-Shadow Address Space |
| MSC | Most-Significant Character |
| MSI | Message-Signaled Interrupt |
| MSIO | Memory Stick Input/Output |
| MSR | Microsoft Reserved Partition |
| MTP | Media Transfer Protocol |
| MTS | Multichannel Television Sound |
| MUFS | Multi-User File System |
| MUI | Multilingual User Interface |
| MUX | MUltipleXer |
| MXC | Media Center Extender |
| MXDW | Microsoft XPS Document Writer |
| NABTS | North American Basic Teletext Specification |
| NAK | Negative AcKnowledgment |
| NAP | Network Access Protection |
| NAS | Network-Attached Storage |