cy·an·o·gen (s?-?n??-j?n)n.1. A colorless, flammable, pungent, highly poisonous gas, C2N2, used as a rocket propellant, an insecticide, and a chemical weapon.2. A univalent CN group found in simple and complex cyanide compounds.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.cyanogen (sa??æn?d??n) n (Elements & Compounds) an extremely poisonous colourless flammable gas with an almond-like odour: has been used in chemical warfare. Formula: (CN)2[C19: from French cyanogène; see cyano-, -gen; so named because it is one of the constituents of Prussian blue]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014cy?an?o?gen (sa??æn ? d??n, -?d??n) n. 1. a colorless, poisonous, flammable gas, C2N2, used chiefly in organic synthesis. 2. the univalent group CN. [1820?30;