/ Dictionary / Index O orthophosphoric acid: Meaning and Definition of Find definitions for: or'tho•phos•phor'ic ac'id Pronunciation: (ôr'thō-fos-fôr'ik, -for'-, ôr"-), [key] — Chem. Chem. a colorless, crystalline solid, HPO, the tribasic acid of pentavalent phosphorus: used chiefly in fertilizers, as a source of phosphorus salts, and in soft drinks as an acidulant and flavoring agent. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. orthophosphate orthophosphorous acid Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language