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

Etymology

Origin of retardant

First recorded in 1635–45; retard + -ant

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

Among the synthetic products, 19 claimed to be flame retardant, three were labeled water resistant, nine advertised heat resistance, and three promoted "green" claims such as "no PVC" or "non-toxic."

From Science Daily • Feb. 19, 2026

Professor Edwin Galea, from the University of Greenwich, said the effectiveness of retardant treatment on PU foam can wear off over time.

From BBC • Jan. 2, 2026

"What that pressure is doing is, it's forcing the fire retardant into the very core of the timber," says Mr McCann.

From BBC • Nov. 6, 2025

As the flames approached, he activated three sprinklers that sprayed fire retardant along the perimeter of the property, keeping the fire at bay.

From Los Angeles Times • Aug. 10, 2025

She fed another bottle to Dodger, then used the last one to wash the fire retardant out of their eyes and off their faces as best she could.

From "Two Degrees" by Alan Gratz