retard

American  

[ri-tahrd, ree-tahrd] / rɪˈtɑrd, ˈri tɑrd /

verb (used with object)

1. to make slow; delay the development or progress of (an action, process, etc.); hinder or impede.

   Synonyms:

   check, obstruct

   Antonyms:

   accelerate

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verb (used without object)

1. to be delayed.

noun

1. a slowing down, diminution, or hindrance, as in a machine.

2. Slang: Disparaging and Offensive.

   1. a contemptuous term used to refer to a person who is cognitively impaired.

   2. a person who is stupid, obtuse, or ineffective in some way.

3. Automotive, Machinery. an adjustment made in the setting of the distributor of an internal-combustion engine so that the spark for ignition in each cylinder is generated later in the cycle.

retard British  

verb

1. (tr) to delay or slow down (the progress, speed, or development) of (something)

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noun

1. offensive a retarded person

2. offensive a foolish person

Sensitive Note

See retarded.

Other Word Forms

• retardingly adverb

Etymology

Origin of retard

First recorded in 1480–90; from Latin retardāre to delay, protract, equivalent to re- re- + tardāre “to loiter, be slow,” derivative of tardus “slow”; tardy

Explanation

To retard something is to slow it down. A lack of fresh fruit and vegetables can retard the growth of a young child. This word should be used with a lot of caution. Using this word to describe a person is considered offensive and should be avoided. It is often a harmless word when used as a verb. While skiing, a heavy, bulky jacket could retard your progress down the mountain. Keeping a plant out of sunlight would retard its growth.

Example Sentences

A case in point is a bill on New York Gov. Kathy Hochul’s desk that would retard artificial intelligence in the name of protecting public safety.

From The Wall Street Journal • Dec. 11, 2025

The giant trees resist burning thanks to the bark, up to about 30 centimeters thick at the base, which contains tannic acids that retard flames.

From Science Magazine • Dec. 1, 2023

"Going forward, we'll be able to do tests on mice to see if new molecules that stabilise mitochondrial and autophagic function can retard the disease."

From Science Daily • Nov. 1, 2023

“Although you may retard an ignition or a fire spread for this season, what you’ve done is grown a lot more biomass to burn in the next year,” he said.

From Los Angeles Times • Jul. 3, 2023

I resolved, therefore, that if my immediate union with my cousin would conduce either to hers or my father’s happiness, my adversary’s designs against my life should not retard it a single hour.

From "Frankenstein" by Mary Shelley

Related Words

• choke off
• crimp
• decelerate
• hamper
• impede
• lessen