Dictionary Check: undercutting

sell cheaper than one's competition

cut away material from the underside of (an object) so as to leave an overhanging portion in relief

cut away the underpart of

strike (the ball) in golf, tennis, or hockey obliquely downward so as to give a backspin or elevation to the shot

cut obliquely into (a tree) below the main cut and on the side toward which the tree will fall