This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. Acting or tending to retard. Often used in combination: flame-retardant pajamas for children; a fire-retardant security chest.

adj. Serving to retard (slow down) the action of something

n. Something that serves to retard (slow down) the action of something

Retarding; tending to delay or impede motion, growth, or progress.

n. any agent that retards or delays or hinders

"FireIceR is a patent pending fire suppressant used for direct attack of fires as well as a medium term retardant for structure protection."

agent   

flame retardant   

ardent   

alcohol-resistant    retardants    fire-retardant    mood-altering    manometer    impingement    defoliant    datingdiscount    mind-altering    sulphury