/ Dictionary / Index A ammonium alum: Meaning and Definition of Find definitions for: ammo'nium al'um Pronunciation: [key] — Chem. Chem. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ammonium acetate ammonium bicarbonate Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language