cut down vs undercut

cut down is not a noun while undercut is a noun.

Word	Noun	Adjective	Verb	Adverb
cut down	No	No	Yes	No
undercut	Yes	No	Yes	No

cut down (noun)	undercut (noun)
	(sports) a stroke that puts reverse spin on the ball
	a cut made underneath to remove material
	a notch cut in the trunk of tree in order to determine the direction of its fall
	the tender meat of the loin muscle on each side of the vertebral column
	the material removed by a cut made underneath

cut down (verb)	undercut (verb)
cut down on; make a reduction in	strike (the ball) in golf, tennis, or hockey obliquely downward so as to give a backspin or elevation to the shot
intercept (a player)	cut away the underpart of
cause to come or go down	cut away material from the underside of (an object) so as to leave an overhanging portion in relief
cut with a blade or mower	cut obliquely into (a tree) below the main cut and on the side toward which the tree will fall
cause to fall by or as if by delivering a blow	sell cheaper than one's competition
cut with sweeping strokes; as with an ax or machete