Warp

Any distortion in the plane of a door itself and not its relationship to the frame or jamb in which it is to be hung. The term warp includes bow, cup and twist, which are defined as follows: Bow-A flat wise deviation from a straight line drawn from top to bottom; a curvature along the length of the door. Cup-A deviation from a straight line drawn from side to side; a curvature along the width of the door. Twist-A deviation in which one or two comers of the door are out of plane with the other comers of the door.