| M&S | Mud and Snow 
| Others |
| M&STL | Minneapolis and St. Louis Railway
| Others |
| M&T | Michigan and Trumbull
| Others |
| M&T | Mud and Terrain
| Others |
| M&TE | Measurement and Test Equipment
| Others |
| M&V | Mission & Vision
| Others |
| M'LADY | My Lady
| Others |
| M(2) | Square Meter
| Others |
| M+C | Medicare+Choice
| Others |
| M+J | Mabey & Johnson
| Others |
| m, min | minimum - a minimum
| Others |
| M- | Mega (1 Million)
| Others |
| M- | Mega (1 Million) (prefix)
| Others |
| M- | Motorway
| Others |
| M- | Time in Days Before Move Operations
| Others |
| M-) | See no evil
| Others |
| M-),:X, :-M | See no evil, hear no evil, speak no evil
| Others |
| M-47 | Dragon Missile
| Others |
| M-ASP | Master Attendant Switch Panel
| Others |
| M-CLASS | Mobile Cross-chain LORAN Atmospheric Sounding System
| Others |
| M-Commerce | Mobile Commerce
| Others |
| M-CSI | Mobility management CAMEL (Customized Applications for Mobile network Enhanced Logic) Subscription Information
| Others |
| M-D | man-day(s)
| Others |
| M-DARC | Military Direct Access Radar Channel
| Others |
| M-DAY | Mobilization DAY
| Others |
| M-Day | Unnamed Day On Which Mobilization of Forces Begins
| Others |
| M-DCPS | Miami-Dade County Public Schools
| Others |
| M-DISC | Millennial Disc
| Others |
| M-E-M | Model-Exercise-Model
| Others |
| M-F | Monday Through Friday
| Others |
| M-FORCE | Master Force
| Others |
| M-H | Man-Hours
| Others |
| M-HSRP | Multiple-Hot Standby Routing Protocol
| Others |
| M-IMS | Market-led International Monetary System
| Others |
| M-KG | Meter-KiloGram
| Others |
| M-Kill | Mobility Kill
| Others |
| M-LEAD | Mouth Lead
| Others |
| M-M | IEEE Micro Magazine
| Others |
| M-M | Multiplex - Multicast
| Others |
| M-M-L-S | Model-Modes-Loads-Stresses
| Others |
| M-NASR | Maine- Niles Association of Special Recreation
| Others |
| M-RETS | Midwest Renewable Energy Tracking System
| Others |
| M-Sand | Manufactured Sand
| Others |
| M-SPEC | Multi-Attraction Spectrum
| Others |
| M-Spike | Monoclonal Spike
| Others |
| M-T-M | Model-Test-Model
| Others |
| M-TAP | Multifunction Target Acquisition Processor
| Others |
| M-TEC | Michigan Technical Education Center
| Others |
| M-TIS | Micro Test Item Stimulator
| Others |
| M-TYPE | Metallic (Asteroid)
| Others |