[until hell freezes over] {adv. phr.}, {slang} Forever, for an eternity. […]

[up a stump] {adj. phr.}, {slang} Stumped; blocked; mixed up or […]

[up front] (1) {n.}, {slang}, {informal} The managerial section of a […]

[up front] (2) {adj.}, {slang}, {informal} Open, sincere, hiding nothing. * […]

[up tight] or [uptight] {adj.}, {slang}, {informal} Worried, irritated, excessively eager […]

[upper story] {n.} 1. A floor or level of a building […]

[ur] "You're" or "your"

[URT] "Urban Terror"; A mod for Quake III

[URYYFM] "You are too wise (two Ys) for me"

[use one's head] or {slang} [use one's bean] or {slang} [use […]