Wiktionary(0.00 / 0 votes)Rate this definition: gridiron(Noun) An instrument of torture on which people were secured before being burned by fire. gridiron(Noun) An iron rack or grate used for broiling flesh and fish over coals. gridiron(Noun) Any object resembling the rack or grate. gridiron(Noun) The field on which American football is played. gridiron(Noun) American football. gridiron(Noun) A generic term for American and Canadian football, particularly when used to distinguish from other codes of football.