/ Dictionary / Index L lepton number: Meaning and Definition of Find definitions for: lep'ton num"ber Pronunciation: [key] — Physics. Physics. in a process involving elementary particles, the total number of leptons minus the total number of antileptons. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. lepton leptophos 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