/ Dictionary / Index C Cys: Meaning and Definition of Find definitions for: Cys Pronunciation: [key] — Biochem. Biochem. cysteine. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Cyrus cyst Related Content Daily Word Quiz: penurious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language