/ Dictionary / Index R renin: Meaning and Definition of Find definitions for: re•nin Pronunciation: (rē'nin), [key] — n. Biochem. a proteolytic enzyme secreted by the kidneys that is involved in the release of angiotensin. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: renin (Thesaurus) reniform renitent Related Content Daily Word Quiz: resilient Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language