/ Dictionary / Index M millimicron: Meaning and Definition of Find definitions for: mil•li•mi•cron Pronunciation: (mil'u-mī"kron), [key] — pl. -crons, -cra a unit of length equal to one thousandth of a micron; one-billionth of a meter. Symbol: m&mgr;&hasp; Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: millimicron (Thesaurus) millimeter millimole 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