/ Dictionary / Index U USM: Meaning and Definition of Find definitions for: USM Pronunciation: [key] United States Mail. United States Marines. United States Mint. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. U.S.L.T.A. U.S.M.A. Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language