/ Dictionary / Index Z Z-zero particle: Meaning and Definition of Find definitions for: Z'-ze'ro par"ticle Pronunciation: (zē'zēr'ō), [key] — Physics. Physics. one of three particles, called intermediate vector bosons, that are believed to transmit the weak force. Symbol: Z Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ZZ ZZZ Related Content Daily Word Quiz: dormant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language