/ Dictionary / Index S sodium thiosulfate: Meaning and Definition of Find definitions for: so'dium thiosul'fate Pronunciation: [key] — Chem. Chem. a white, crystalline, water-soluble powder, NaSO&multiplydot;5HO, used as a bleach and in photography as a fixing agent. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sodium thiopental sodium tripolyphosphate Related Content Daily Word Quiz: laudable Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language