retard

1 of 3

verb

re·​tard ri-ˈtärd 

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

retard

2 of 3

noun (1)

re·​tard

plural retards

1

ri-ˈtärd  : a holding back or slowing down : retardation

2

ˈrē-ˌtärd  offensive : a person affected with intellectual disability

3

ˈrē-ˌtärd  informal + offensive : a foolish or stupid person

retarder

3 of 3

noun (2)

re·​tard·​er

rə̇ˈtärdər, 

rēˈ-, 

-tȧdə(r

plural -s

: one that retards: such as

a

: a substance that when added to a cement or to gypsum plaster prolongs the setting time

b

: restrainer

c

: a power-operated braking device placed in the classification tracks of hump yards to control the speed of moving railroad cars

d

: a substance added in small proportion to a rubber compound for retarding vulcanization

Synonyms of retard

Verb

• slow
• brake

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

Verb

As engine revs increase, centrifugal force alters the valve timing by a few degrees, either advancing or retarding it. — Utkarsh Sood june 17, New Atlas, 17 June 2025

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

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

But that approach is rather slow to respond and is limited to applying retarding force. — IEEE Spectrum, 26 June 2018

Blockchain thus provides companies and banks a way to undo Basel II’s and Basel III’s retarding effect on trade finance while complying with their requirements. — Rebecca Liao, Foreign Affairs, 16 Aug. 2017

Word History

Etymology

Verb and Noun (2)

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

First Known Use

Verb

15th century, in the meaning defined at transitive sense

Noun (1)

1781, in the meaning defined at sense 1

Rhymes for retard

• asgard
• backyard
• barnyard
• blackguard
• bombard
• brickyard
• canard
• churchyard
• coastguard
• courtyard
• debarred
• diehard

Kids Definition

retard

verb

re·​tard

ri-ˈtärd

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

retarder noun

Medical Definition

retard

transitive verb

re·​tard ri-ˈtärd 

: to slow up especially by preventing or hindering advance or development

retard spoilage

retard hair loss