/ Dictionary / Index R restriction enzyme: Meaning and Definition of Find definitions for: restric'tion en"zyme Pronunciation: [key] — Biochem. Biochem. any of a group of enzymes that catalyze the cleavage of DNA molecules at specific sites: used for gene splicing in recombinant DNA technology and for chromosome mapping. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. restriction restriction fragment Related Content Daily Word Quiz: vertigo Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language