in·hib·i·tor also in·hib·it·er (?n-h?b??-t?r)n. One that inhibits, as a substance that retards or stops a chemical reaction.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.inhibitor (?n?h?b?t?) n1. Also called: inhibiter a person or thing that inhibits2. (Chemistry) Also called: anticatalyst a substance that retards or stops a chemical reaction. Compare catalyst3. (Biochemistry) biochem a. a substance that inhibits the action of an enzymeb. a substance that inhibits a metabolic or physiological process: a plant growth inhibitor. 4. (General Physics) any impurity in a solid that prevents luminescence5. (Astronautics) an inert substance added to some rocket fuels to inhibit ignition on certain surfacesCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014in?hib?i?tor or in?hib?it?er (?n?h?b ? t?r) n. 1. one that inhibits. 2. a substance that slows or stops a chemical reaction. [1865?70] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.