/ Dictionary / Index N natural killer cell: Meaning and Definition of Find definitions for: nat'ural kill'er cell" Pronunciation: [key] — Immunol. Immunol. a small killer cell that destroys virus-infected cells or tumor cells without activation by an immune system cell or antibody. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. naturalize natural language Related Content Daily Word Quiz: candor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language