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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


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.

See Examples For:

Its firefighting fleet also includes Dash 8 water-bombing planes, which can drop more than 2,600 gallons of water or fire retardant.

From The Wall Street Journal ● Jul. 30, 2026

Planes often fly in a continuous shuttle while retardant is laid along the edges of the fire and ground crews attack the flames directly.

From BBC ● Jul. 27, 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

If the cameras and heat sensors around the house detect danger, the system can envelop the home in over 1,000 gallons of fire retardant and hundreds of gallons of fire-suppressing foam.

From Los Angeles Times ● Mar. 2, 2026

Her eyes were weeping from the fire retardant, and she barely got them open in time to see the tree branch in front of her.

From "Two Degrees" by Alan Gratz

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