/ Dictionary / Index N nuclear family: Meaning and Definition of Find definitions for: nu'clear fam'ily Pronunciation: [key] a social unit composed of father, mother, and children. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. nuclear energy nuclear fission 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