/ Dictionary / Index M milliroentgen: Meaning and Definition of Find definitions for: mil•li•roent•gen Pronunciation: (mil'u-rent"gun, -jun, -runt"-), [key] — n. a unit of radiation equal to one thousandth of a roentgen. Abbr.: mR, mr Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. millirem millisecond Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language