/ Dictionary / Index N neutron number: Meaning and Definition of Find definitions for: neu'tron num"ber Pronunciation: [key] — Physics. Physics. the number of neutrons in the nucleus of an atom, equal to the mass number minus the atomic number of the atom. Symbol: N Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. neutron bomb neutron star Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language