/ Dictionary / Index H hypophosphorous acid: Meaning and Definition of Find definitions for: hy'pophos'phorous ac'id Pronunciation: [key] a colorless or yellowish, water-soluble, liquid, monobasic acid, HPO, having a sour odor, and used as a reducing agent. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. hypophosphorous hypophrygian mode Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language