/ Dictionary / Index T tau lepton: Meaning and Definition of Find definitions for: tau' lep"ton Pronunciation: [key] — Physics. Physics. an unstable lepton with a mass approximately 3500 times that of the electron. Symbol: T Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. taught tau neutrino Related Content Daily Word Quiz: penchant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language