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retardant

American  
[ri-tahr-dnt] / rɪˈtɑr dnt /

noun

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


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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

adjective

  1. having a slowing effect

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms

Derived Forms

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."

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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

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

Ventura County fire officials said they followed protocol when they left the Balcom fire — clearing containment lines, dropping retardant, and using a drone with an infrared camera to identify lingering heat.

From Los Angeles Times • Jan. 30, 2026

Fire crews typically use tanker trucks to bring water, and also rely on helicopters and planes to drop water and retardant on fires.

From Los Angeles Times • Dec. 17, 2025

The firefighters now directed all their attention to adjacent buildings, hosing down nearby roofs with fire retardant.

From "Scythe" by Neal Shusterman

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