| M | Meter(s) | - | Scuba Diving |
| MAMS | Multispectral Atmospheric Mapping Sensor | - | Scuba Diving |
| MAS | MODIS Airborne Simulator | - | Scuba Diving |
| MB | Millibar(s) | - | Scuba Diving |
| MB OR MB | Megabytes (or Megabits) | - | Scuba Diving |
| MB/S | Megabytes Per Second | - | Scuba Diving |
| MCIDAS | Man Computer Interactive Data Access System | - | Scuba Diving |
| METEOSAT | METEOrological SATellite (European) | - | Scuba Diving |
| MHZ | MegaHertz | - | Scuba Diving |
| MISR | Multi-angle Imaging Spectro-Radiometer (EOS) | - | Scuba Diving |
| MLS | Microwave Limb Sounder (EOS) | - | Scuba Diving |
| MODIS | MODerate-resolution Imaging Spectroradiometer (EOS) | - | Scuba Diving |
| MODIS-N | MODerate-resolution Imaging Spectroradiometer-Nadir (EOS) | - | Scuba Diving |
| MOPITT | Measurements Of Pollution In The Troposphere (EOS) | - | Scuba Diving |
| MSG | Meteosat Second Generation | - | Scuba Diving |
| MSL | Mean Sea Level | - | Scuba Diving |
| MSLP | MSL Pressure | - | Scuba Diving |
| MSS | Multi-Spectral Scanner | - | Scuba Diving |
