Definition of header

• n. - One who, or that which, heads nails, rivets, etc., esp. a machine for heading.
• n. - One who heads a movement, a party, or a mob; head; chief; leader.
• n. - A brick or stone laid with its shorter face or head in the surface of the wall.
• n. - In framing, the piece of timber fitted between two trimmers, and supported by them, and carrying the ends of the tailpieces.
• n. - A reaper for wheat, that cuts off the heads only.
• n. - A fall or plunge headforemost, as while riding a bicycle, or in bathing; as, to take a header.