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

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

"These resources can access remote and rugged terrains, dropping water and fire retardant directly on the fire's critical areas, something that ground forces might struggle with in vast and challenging landscapes like Rhinogydd," she said.

From BBC ● Jul. 22, 2026

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

From The Wall Street Journal ● Jun. 23, 2026

Sunshine Silver Mining & Refining, which also mines copper and antimony, a flame retardant mineral, could be a backdoor AI play given the demand for wiring in data centers.

From Barron's ● Jun. 2, 2026

The fire retardant hadn’t hit that spot, and something there seethed and burned.

From "Two Degrees" by Alan Gratz

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