/ Dictionary / Index M microsecond: Meaning and Definition of Find definitions for: mi•cro•sec•ond Pronunciation: (mī'kru-sek"und), [key] — n. a unit of time equal to one millionth of a second. Symbol: &mgr;sec Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: microsecond (Thesaurus) microscopy microsegment 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