Pronunciation: (u-mōn'yu, u-mō'nē-u),[key] —n.Chem. 1. a colorless, pungent, suffocating, highly water-soluble, gaseous compound, NH3, usually produced by the direct combination of nitrogen and hydrogen gases: used chiefly for refrigeration and in the manufacture of commercial chemicals and laboratory reagents.
2. Also called ammonia solution, ammonia water, aqua ammoniae, aqua ammonia, aqueous ammonia. this gas dissolved in water; ammonium hydroxide.