uncock-- To straighten the wrists during downward portion of the golf swing.
underclubbing-- To accidentally choose a club that will not travel the desired distance.
underspin-- When the golf ball flies toward the target while rotating about its axis away from the target from the bottom to the top. Underspin is also called backspin.
unplayable lie-- A ball which is in a position that can't be played such as in a bush or tree.
up-- As in "get up", meaning travel up to hole level or the intended target area.
up-- The number of strokes or points a player is up versus an opponent. For example, "Nicklaus is up 3 with 5 holes remaining."
up and down-- Hitting a ball out of a sand trap, rough or other difficult area and still salvaging a par.
upright swing-- Type of swing in which the clubhead travels more directly backward and upward from the golfball.
USGA-- Acronym for United States Golf Association. The USGA is the official governing body for golf rules in the United States.