/ Dictionary / Index M millimeter: Meaning and Definition of Find definitions for: mil•li•me•ter Pronunciation: (mil'u-mē"tur), [key] — n. a unit of length equal to one thousandth of a meter and equivalent to 0.03937 inch. Abbr.: mm Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: millimeter (Thesaurus) millime millimicron Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language