header meaning
Webster Dictionary(0.00 / 0 votes)Rate this definition: 1  Header(noun) one who, or that which, heads nails, rivets, etc., esp. a machine for heading. 2  Header(noun) one who heads a movement, a party, or a mob; head; chief; leader. 3  Header(noun) a brick or stone laid with its shorter face or head in the surface of the wall.