retardant

American  

[ri-tahr-dnt] / rɪˈtɑr dnt /

noun

Chemistry.

1. any substance capable of reducing the speed of a given reaction.

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adjective

1. retarding or tending to retard (usually used in combination).

   fire-retardant construction materials.

retardant British  

/ rɪˈtɑːdənt /

noun

1. a substance that reduces the rate of a chemical reaction

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adjective

1. having a slowing effect

Other Word Forms

• retardance
  noun
• retardancy
  noun

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Etymology

Origin of retardant

First recorded in 1635–45; retard + -ant

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Explanation

A retardant is anything that prevents something from happening, or inhibits it from growing or spreading. Using a rust retardant on your car, for example, should help keep it from getting rusty. A fire or flame retardant is a type of chemical that stops fire from starting or spreading. Sometimes fire retardants are sprayed or dumped on a fire to put it out, like the foam fire retardant you might spray from a hand-held fire extinguisher onto a grease fire in a kitchen. Retardant comes from the verb retard, "make slow, or make slower."

Example Sentences

See Examples For:

retardant

Firefighters continue a battle against the blaze that includes use of helicopter water drops and retardant, Cal Fire said.

From Los Angeles Times ● Aug. 22, 2026

Aircraft dropped water and flame retardant from above, while ground crews built firebreaks with equipment ranging from bulldozers to hand tools.

From Science Daily ● Aug. 5, 2026

A succession of helicopters then follows with their own streams of red fire retardant.

From BBC ● Jul. 29, 2026

I pay for a private fire department, and we have built-in retardant sprayers.

From The Wall Street Journal ● Jun. 23, 2026

When at last she wrenched her eyes open, Akira found herself staring straight up into the face of Dodger, who was coated all over in bright red fire retardant.

From "Two Degrees" by Alan Gratz

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