underclubbing Using a club that does not give the needed distance

underspin Same as backspin.

unplayable lie A lie in which the ball is impossible to play such as in a thicket of trees.

up A shot reaching at least as far as the hole.

up A specified number of strokes you are ahead of your opponent in match play.

up and down Getting out of trouble or out of a hazard and into the hole.

upright swing A swing that carries the club head more directly backward and upward from the ball.

USGA United States Golf Association.