am·mo·nia (?-m?n?y?)n.1. A colorless, pungent gas, NH3, extensively used to manufacture fertilizers and a wide variety of nitrogen-containing organic and inorganic chemicals.2. See ammonium hydroxide.[New Latin, from Latin (s?l) amm?niacus, (salt) of Amen, from Greek Amm?niakos, from Amm?n, Amun (from its having been obtained from a region near the temple of Amun, in Libya), from Egyptian jmn.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.ammonia (??m??n??; -nj?) n1. (Elements & Compounds) a colourless pungent highly soluble gas mainly used in the manufacture of fertilizers, nitric acid, and other nitrogenous compounds, and as a refrigerant and solvent. Formula: NH32. (Elements & Compounds) a solution of ammonia in water, containing the compound ammonium hydroxide[C18: from New Latin, from Latin (sal) amm?niacus (sal) ammoniac1]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014am?mo?nia (??mo?n y?, ??mo? ni ?) n. 1. a colorless, pungent, suffocating, highly water-soluble, gaseous compound, NH3, used chiefly for refrigeration and in the manufacture of commercial chemicals and laboratory reagents. 2. Also called ammonia water. ammonia dissolved in water; ammonium hydroxide. [1790?1800;