| Acronym | Definition |
|---|
| M | Middle |
| M | 1000 (Roman numeral) |
| M | Monthly |
| M | Male |
| M | Monsieur |
| m | Meter (SI unit of length) |
| M | Mega- (Million) |
| M | Media |
| M | Music |
| M | Management |
| M | Member |
| M | Money |
| M | Mean (arithmetic average; math; statistics) |
| M | Million |
| M | Materials |
| M | Master |
| M | Multi |
| M | Mike (Alabama Public Safety Radio Code) |
| M | Machine |
| M | Modified |
| M | Mission |
| M | Missing |
| M | Mass (as in E=mc^2) |
| M | Museum |
| M | Medium |
| M | Manual |
| M | Minor (IRB) |
| M | Meta (benzene) |
| M | Metro (Washington DC public transit) |
| M | Marine (German) |
| M | Married (with spouse) |
| M | Mouth |
| M | Milwaukee (ammunition headstamp) |
| M | Manager (baseball) |
| M | Manchester (postcode, United Kingdom) |
| M | Magnetic |
| M | Mandatory |
| M | Momentum |
| M | Military (Scott Catalogue prefix; philately) |
| M | Millennium |
| M | Mint |
| M | Magenta |
| M | Slope |
| M | Module (abstract algebra, mathematical object) |
| M | Mach (multiple of speed of sound) |
| M | Motorsport (BMW) |
| M | Medley |
| M | Murderer (from the Movie M) |
| m | Milli- |
| M | Misdemeanor |
| M | Magnitude (Richter scale) |
| M | Unfounded (Alabama Public Safety Radio Code) |
| M | Munich (auto license plate) |
| M | Methionine (amino acid) |
| M | Messier (Cataloguer of Stellar Objects) |
| M | Mechanized |
| M | Maintainability |
| m | micrometer |
| M | Marquess (British title of nobility) |
| M | Metropolitano (Lisbon underground) |
| M | US Marine Corps |
| M | Moderate Risk |
| M | Matrix Protein (virus protein) |
| M | Metro Toronto (postal code designation, Canada) |
| M | Minesweeper (Navy vessel) |
| M | Multisource |
| M | Molarity |
| M | Mesial |
| M | Multimission (US military aircraft modified mission symbol) |
| M | Moment Magnitude |
| M | Multipara |
| M | Moderata Samlingspartiet (Swedish political party) |
| M | Mobility Ratio |
| M | Mole/Molar |
| M | Measured Ceiling (weather reports) |
| M | Metroad (Australian road system) |
| M | Mature Age 17+ (ESRB; game rating) |
| M | Mid-Course Update |
| M | Modifier Function Bit |
| M | Myasistchev (Soviet aircraft designer) |
| M | Objective C Implementation File (file extension) |
| M | Motormännens Riksorganisation (Swedish automobile owners association) |
| M | Manual Tuned NAVAID |
| M | US DoT tire speed rating (81 mph) |
| M | Chief of the British Secret Service, MI6 (in James Bond Films) |