(adj.) : serving or tending to retard ; - retardant noun (Date: 1642) (Merriam-Webster's Unabridged at www.m-w.com) (Note: FIREWISE defines retardant as: substance or chemical agent which reduces the flammability of combustibles.)

any agent that retards or delays or hinders; "flame-retardant"

A substance or chemical agent which reduced the flammability of combustibles.

A substance which will slow or stop fire spread.

A chemical sometimes added to cement or mortar to slow the rate of setting.

See Mud.