/ Dictionary / Index S sodium tripolyphosphate: Meaning and Definition of Find definitions for: so'dium tri•pol•y•phos'phate Pronunciation: (trī"pol-ē-fos'fāt), [key] — Chem. Chem. a white powder, NaPO, used as a water softener, sequestering agent, and food additive. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sodium thiosulfate sodium-vapor lamp Related Content Daily Word Quiz: nefarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language