1 of 2


re·​tard ri-ˈtärd How to pronounce retard (audio)
retarded; retarding; retards

transitive verb

: to delay or impede the development or progress of : to slow up especially by preventing or hindering advance or accomplishment
chemicals to retard the spread of fire

intransitive verb

: to become delayed : to undergo retardation
retarder noun


2 of 2


plural retards
ri-ˈtärd How to pronounce retard (audio) : a holding back or slowing down : retardation
ˈrē-ˌtärd How to pronounce retard (audio) offensive : a person affected with intellectual disability
ˈrē-ˌtärd How to pronounce retard (audio) informal + offensive : a foolish or stupid person
Choose the Right Synonym for retard

delay, retard, slow, slacken, detain mean to cause to be late or behind in movement or progress.

delay implies a holding back, usually by interference, from completion or arrival.

bad weather delayed our arrival

retard suggests reduction of speed without actual stopping.

treatment that retards tumor growth

slow and slacken also imply a reduction of speed, slow often suggesting deliberate intention

she closed her eyes and slowed her breathing

, slacken an easing up or relaxing of power or effort.

on hot days runners slacken their pace

detain implies a holding back beyond a reasonable or appointed time.

unexpected business had detained her

Examples of retard in a Sentence

Verb The chemical will retard the spread of fire. The problems have retarded the progress of the program.
Recent Examples on the Web
Turning the lithium oxide—the product of discharging the battery—back to lithium is difficult and only partially possible even when assisted by special catalysts: The oxide builds up and retards the process, limiting the number of charge-discharge cycles to a mere handful. IEEE Spectrum, 31 Jan. 2011 Genesis Yes, the thing retarding recruitment below pre-2022 levels may be, at least in part, a military-wide health-records update that, much like MyChart in the civilian health-care world, tracks the medications of all service members. Luther Ray Abel, National Review, 9 Feb. 2024 Traditional concern with fiscal deficits has focused on their impact in pushing up interest rates and retarding investment. Lawrence H. Summers, Foreign Affairs, 15 Feb. 2016 It can be combatted by at least three means: by adding water injection, which Pontiac has avoided for a number of good reasons; by enriching the fuel-air mixture, which is unfortunately contrary to efficiency goals and therefore used sparingly; and by retarding ignition timing. Don Sherman, Car and Driver, 1 May 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'retard.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History



Middle English, from Anglo-French or Latin; Anglo-French retarder, from Latin retardare, from re- + tardus slow

First Known Use


15th century, in the meaning defined at transitive sense


1781, in the meaning defined at sense 1

Time Traveler
The first known use of retard was in the 15th century

Dictionary Entries Near retard

Cite this Entry

“Retard.” Dictionary, Merriam-Webster, Accessed 20 Apr. 2024.

Kids Definition


: to slow up especially by preventing or checking progress : hinder
retarder noun

Medical Definition


transitive verb
re·​tard ri-ˈtärd How to pronounce retard (audio)
: to slow up especially by preventing or hindering advance or development
retard spoilage
retard hair loss
Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!