/ Dictionary / Index H hydroxylase: Meaning and Definition of Find definitions for: hy•drox•y•lase Pronunciation: (hī-drok'su-lās", -lāz"), [key] — n. Biochem. any enzyme that catalyzes the introduction of a hydroxyl group into a substance. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. hydroxylamine hydroxyl group Related Content Daily Word Quiz: abstain Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language