/ Dictionary / Index U u quark: Meaning and Definition of Find definitions for: u quark Pronunciation: [key] — Physics. Physics. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. upwind Ur 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