pel·ar·gon·ic acid (p?l?är-g?n??k, -g??n?k)n. A colorless or yellow oil, C9H18O2, used in the manufacture of lacquers, plastics, and pharmaceuticals. Also called nonanoic acid.[pelargon(ium) + -ic.]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.pelargonic acid (?p?l????n?k) n (Elements & Compounds) another name for nonanoic acid[C19: so named because it was originally derived from pelargonium leaves]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014