/ Dictionary / Index N nuclear fission: Meaning and Definition of Find definitions for: nu'clear fis'sion Pronunciation: [key] fission (def. 2). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. nuclear family nuclear fuel Related Content Daily Word Quiz: deleterious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language