| Term | Definition |
| mausoleum | monumental tomb |
| mauve | pale purple |
| maverick | rebel; nonconformist |
| mawkish | Excessively and objectionably sentimental; mushy and gushy; icky-sticky sentimental; maudlin |
| maxim | proverb; a truth pithily stated |
| mayhem | injury to body |
| meager | scanty; inadequate |
| mealymouthed | indirect in speech; hypocritical; evasive |
| meander | wind or turn in its course |
| meddlesome | interfering |
| mediate | settle a dispute through the service of an outsider |
| mediocre | ordinary; commonplace |
| meditation | reflection; thought |
| medium (1) | element that is a creature's natural environment; nutrient setting in which microorganisms are cultivated |
| medium (2) | appropriate occupation or means of expression; channel of communication; compromise |
| medley | mixture |
| meek | submissive; patient and long-suffering |
| megalomania | mania for doing grandiose things; An obsession with grandiose or extravagant things or actions |
| melancholy | gloomy; morose; blue; Tending to promote sadness or gloom: |
| melee | fight |
| mellifluous | sweetly or smoothly flowing; melodious; pleasing to the ear |
| memento | token; reminder |
| memorialize | commemorate |
| menagerie | collection of wild animals |
| mendacious | lying; habitually dishonest |
| mendicant | beggar |
| menial | suitable for servant; lowly; mean |
| mentor | counselor; teacher |
| mercantile | concerning trade |
| mercenary | motivated solely by money or gain |
| mercurial | capricious; changing; fickle |
| meretricious | flashy; tawdry; Tastelessly showy |
| merger | combination (of two business corporations) |
| mesmerize | hypnotize |
| metallurgical | pertaining to the art of removing metals from ores |
| metamorphosis | change of form |
| metaphor | implied comparison |
| metaphysical | pertaining to speculative philosophy |
| mete | measure; distribute |
| meteoric | swift; momentarily brilliant |
| methodical | systematic |
| meticulous | excessively careful; painstaking; scrupulous |
| metropolis | large city |
| mettle | courage; spirit |
| miasma | swamp gas; heavy vaporous atmosphere often emanating from decaying matter; pervasive corrupting influence |
| microcosm | small world; the world in miniature |
| migrant | changing its habitat; wondering |
| migratory | wandering |
| milieu | environment; means of expression |
| militant | combative; bellicose |
| militate | work against |
| millennium | thousand-year period; period of happiness and prosperity |
| mimicry | imitation |
| minatory | menacing; threatening |
| mincing | affectedly dainty |
| minion | servile dependent; An obsequious follower or dependent; a sycophant |
| minuscule | extremely small |
| minute | extremely small |
| minutiae | petty details |
| mirage | unreal reflection; optical illusion |
| mire | entangle; stick in a swampy ground |
| mirth | merriment; laughter |
| misadventure | mischance; ill luck |
| misanthrope | one who hate mankind |
| misapprehension | error; misunderstanding |
| miscellany | mixture of writings on various subjects |
| mischance | ill luck; An unfortunate occurrence; bad luck |
| misconstrue | interpret incorrectly; misjudge |
| miscreant | wretch; villain; evildoer |
| misdemeanor | minor crime |
| miserly | stingy; mean |
| misgivings | doubts |
| mishap | accident |
| misnomer | wrong name; incorrect designation |