rudder
rud.der \'r*d-*r\ n [ME rother, fr. OE ro-ther paddle; akin to OE ro-wan to] row 1a: a flat piece or structure of wood or metal attached upright to a ship's stern so that it can be turned causing the ship's head to turn in the same direction 1b: a movable auxiliary airfoil usu. attached at the rear end that serves t o control direction of flight of an airplane in the horizontal plane 2: GUIDE, GOVERNOR