retarder

[ ri-tahr-der ]
/ rɪˈtɑr dər /

noun

a person or thing that retards.
Chemistry.
  1. any substance added to rubber to delay or prevent vulcanization.
  2. any substance added to delay a process.
Building Trades. an admixture of concrete or plaster that retards its set.

Origin of retarder

First recorded in 1635–45; retard + -er1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

British Dictionary definitions for retarder

retarder
/ (rɪˈtɑːdə) /

noun

a person or thing that retards
a substance added to slow down the rate of a chemical change, such as one added to cement to delay its setting
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