/ Dictionary / Index S selenious acid: Meaning and Definition of Find definitions for: sele'nious ac'id Pronunciation: [key] — Chem. Chem. a colorless, crystalline, water-soluble, poisonous powder, HSeO, used chiefly as a reagent. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. selenious selenite Related Content Daily Word Quiz: illegible Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language