/ Dictionary / Index A ammonium sulfate: Meaning and Definition of Find definitions for: ammo'nium sul'fate Pronunciation: [key] — Chem. Chem. a white, crystalline, water-soluble solid, (NH)SO, used chiefly as a fertilizer. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ammonium stearate ammonium thiocyanate Related Content Daily Word Quiz: mamba Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language