/ Dictionary / Index U USPO: Meaning and Definition of Find definitions for: USPO Pronunciation: [key] United States Post Office. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. USPHS USPS 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