| minatory | Expressing or conveying a threat | |
| mimetic | Relating to, constituting, or habitually practicing imitation or mimicry | |
| milieu | A person's social environment or setting | |
| microcosm | A small, representative system having analogies to a larger system in constitution, configuration, or development | |
| miasma | A highly unpleasant or unhealthy smell or vapor | |
| mettle | A person's ability to cope well with difficulties or to face a demanding situation in a spirited and resilient way | |
| meticulous | Showing great attention to detail; very careful and precise | |
| meteorological | Relating to the study of the atmosphere and the various phenomena associated with it, such as weather and climate. | |
| meretricious | Apparently attractive but having in reality no value or integrity | |
| mercurial | characterized by rapid and unpredictable changes in mood | |