noun Chemistry.

any substance capable of reducing the speed of a given reaction.


retarding or tending to retard (usually used in combination): fire-retardant construction materials.

Origin of retardant

First recorded in 1635–45; retard + -ant
Related formsre·tard·ance, re·tard·an·cy, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for retardant



a substance that reduces the rate of a chemical reaction


having a slowing effect
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for retardant

1640s, from retard (v.) + -ant or from Latin retardantem (nominative retardans), present participle of retardare. From 1952 as a noun, "retardant substance."

Online Etymology Dictionary, © 2010 Douglas Harper