- merman
- mediocre
- mesh
- mature
- mesquite
- masterful
- meteorology
- methodologist
- masculine
- mew
- mewl
- misapprehensive
- microbial
- microfilm
- microscopic
- microsoft
- mid-day nap
- mid-on
- midden
- marginal
- malinger
- malaise
- make someone's hackles rise
- misandry
- middle-east
- militate against
- milk food
- milk skin
- milky
- milky way
- milliard
- millibar
- mimosa pudica
- minatory
- mind one's own business
- musk-deer
- make the grade
- minutiae
- minx
- mirthful
- misadventure
- misanthrope
- misapply
- misapprehension
- miscarry
- miscellaneous
- miscellany
- misinformation
- mentally
- mismatched
- misprint
- mirror
- mystery
- mitochondria
- mix something up
- mycology
- mixed up in
- mixture
- mixy-maxy
- muzzle
- mutual
- mob
- mobile
- mutilate
- muster in force
- muss
- molecular biology
- moleskin
- molest
- mollusc
- molluscum contagiosum
- molotov cocktail
- moment
- monandry
- muddle along, muddle through
- muddle
- monocot
- monodrama
- monogamist
- monopolist
- monosyllable
- monotheistic
- monotone
- monotonous
- moral law
- muck something up
- morass
- much of muchness
- mph
- more information
- more kicks than half penny
- moulder
- more or less
- miraculous
- morbific
- motion
- motionless
- motive
- morbid protruberance of liver
- much awaited