/ Dictionary / Index C cytotoxin: Meaning and Definition of Find definitions for: cy•to•tox•in Pronunciation: (sī"tu-tok'sin), [key] — n. Immunol., Pharm. a substance that has a toxic effect on certain cells. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: cytotoxin (Thesaurus) cytotoxic T cell cytotropic Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language