| Abbreviation | Definition |
|---|---|
| MRX | Mister X |
| MS | Martha Stewart |
| MS | Matthieu Scherrer |
| MS | Max Schonfield |
| MS | Michael Schumacher |
| MS | Mohammed Saber |
| MSA | Michael S. Adler |
| MT | Margaret Thatcher |
| MT | Mike Trout |
| MTJ | Montana Jack |
| MTM | Mary Tyler Moore |
| MU | Mr Utley |
| MVB | Martin Van Buren (1837-1841) |
| MVB | Mike Van Bremen (racing) |
| MVH | Mark Victor Hansen |
| MW | Mann Whitney |
| MW | Mark West |
| MW | Mike Wheeler |
| MW | Mike White |
| MWB | Margaret Wise Brown |