• synonyms


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

First recorded in 1635–45; retard + -er1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for retarder


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


1640s, agent noun from retard (v.). Of railway braking mechanisms from 1937.

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Online Etymology Dictionary, © 2010 Douglas Harper