Mat1  —n. 1 small piece of coarse material on a floor, esp. For wiping one's shoes on. 2 piece of cork, rubber, etc., to protect a surface from a hot dish etc. Placed on it. 3 padded floor covering in gymnastics, wrestling, etc. —v. (-tt-) (esp. As matted adj.) Entangle or become entangled in a thick mass (matted hair).  on the mat slang being reprimanded. [old english]