| mortmain | n. | inalienable ownership | ||
| mossbonker | n. | menhaden, small pelagic fish | ||
| MOT | n. | Ministry of Transport (now the Department of Transport) test of a vehicle’s safety and roadworthiness | British | |
| motivic | adj. | of or related to a motif, used as a motif | ||
| motorik | n. | driving 4/4 beat—often with pop! on 3rd beat—typical of krautrock | ||
| mouchard | n. | nark, police spy | ||
| moulinet | n. | circular cut in fencing; circling an opponent’s blade with your own | ||
| mouse | n. | black eye | slang | |
| moxibustion | n. | burning dried mugwort close to the skin, often along acupuncture meridians, to facilitate healing in Chinese medicine | ||
| mucilage | n. | sticky stuff | ||
| muddlehead | n. | stupid person | ||
| muffetee | n. | small wrist muff | ||
| mugfaker | n. | street photographer | slang | |
| mugient | adj. | bellowing | ||
| mulct | v. | to fine, to impose a penalty; to take by fraud, to swindle | ||
| muleteer | n. | mule driver | ||
| mulligrubs | n. | grumpiness; depressed state; bad mood or temper | ||
| mullion | n. | vertical bar dividing lights in a window or similar panels | ||
| mumble | v. | to chew near uselessly, as with toothless gums | ||
| muniment | n. | document establishing claim to rights or privileges (usu. in plural); means of defense or protection | ||
| munity | n. | bestowed privilege | ||
| munted | adj. | drunk; intoxicated; severely damaged; disgusting | slang | |
| murgeon | v. | to mock, to make faces, to grumble; grimace, wry face | Scots | |
| muriatic acid | n. | hydrochloric acid | ||
| murine | adj. | of or related to mice or similar rodents | ||
| murmuration | n. | flock of starlings (sometimes applied to other birds) | ||
| murrain | n. | cattle disease; [obsolete] plague | ||
| murrey | n. | purple-red | ||
| musette | n. | small knapsack; French bellows-driven bagpipe of the 17th and 18th centuries | ||
| mushrump | n. | mushroom; upstart, arriviste | archaic | |
| muskeg | n. | North American swamp or bog | ||
| muslin | n. | plain weave cotton fabric | ||
| musquash | n. | muskrat | archaic | |
| mussitation | n. | silent movement of the lips without accompanying sound; muttering | ||
| must | n. | new wine, not yet fermented fruit juice | ||
| musteefino | n. | person with 1/16 black ancestry, child of a mustee and a white person | ||
| musth | n. | period of heightened aggressiveness and sexual activity in male elephants | ||
| mutatis mutandis | adv. | with the necessary changes | Latin | |
| muzzy | adj. | blurry, fuzzy, unfocused; confused, dazed; drunk, mentally impaired due to alcohol | ||
| mydriasis | n. | overlarge pupil dilation | ||
| myology | n. | study of muscles and their structures | biology | |
| myrmecology | n. | the study of ants and termites | ||
| myrmidon | n. | blindly loyal follower and carryer-out of a leader’s orders | ||
| mythomane | n. | habitual liar, person compelled to fantasy or exaggeration | ||
| mythopoesis | n. | myth creation | ||
| n.b.g. | adj. | no bloody good | slang | |
| naff | adj. | vulgar, tasteless | British | |
| naker | n. | kettledrum | ||
| nankeen | n. | naturally yellow cotton fabric from China; cotton dyed yellow; yellow or buff color | ||
| Nansen passport | n. | passports issued under the auspices of the League of Nations for stateless persons after World War I |
