A dictionary of slang - "U" - Slang and colloquialisms of the UK.

u-ee	Noun. A u-turn. A term used by drivers.
ugly as sin	Phrs. Very ugly.
umpteen	Adj. Many, a lot of. E.g."There was umpteen colours to choose from."
Uncle Dick	Adj. Sick, unwell. Rhyming slang.
Uncle Ned	Noun. 1. The head. Rhyming slang. 2. Bed. Rhyming slang.
Uncle Tom	Noun. A black person. Derog./Offens.
undercarriage	Noun. The male or female genitals.
undercrackers	Noun. Underpants.
underkecks	Noun. Underpants.
under the weather	Phrs. Out of sorts, not currently in good health. {Informal}
unhinged	Adj. Insane, mentally unstable and unpredictable.
uni	Noun. Abb. of university.
unmentionables	Noun. 1. A coy euphemism for undergarments. [1900s] 2. A coy euphemism for genitals.
unreal	Adj. Fantastic, excellent, wonderful. An expression of approval. [Orig. U.S.]
up	Adj. Intoxicated by drugs, high.
up and down like a whore's drawers	Phrs. Of a person, unsettled, agitated, unrestful. Numerous variations exist, i.e. whore may be replaced by prostitute or tart, and drawers with knickers.
up and down like Tower Bridge	Phrs. 1. Fluctuating, moving up and down. 2. Emotionally unstable
upchuck *	Noun. Vomit. Verb. To vomit. * From 'chuck up', meaning to vomit.
up for it	Phrs. Phrase encompassing the enthusiasm of a person for an event. Particularly evident within the British club scene in the 1990s with the crowd being 'up for it'.
uphill gardener	Noun. A homosexual male.
up on blocks	Phrs. Of a woman, menstruating and therefore unavailable for sex. From being out of service and unusable, like a vehicle in for repair.
upper	Noun. A stimulant drug, usually amphetamine sulphate.
up shit creek	Phrs. In serious trouble. An adaptation of the saying 'up the creek without a paddle', meaning the same.
up sticks	Verb. To move on, to settle or live elsewhere. {Informal}
up the duff	Phrs. Pregnant.
up the pictures	Phrs. Broken, not in working order. E.g."My cooker is up the pictures at the moment, so we'll have to eat out."
up the spout	Phrs. Pregnant.
up the suff	Phrs. 1. Down the drain. [W. Midlands use] 2. Wasted, broken. [W. Midlands use]
up the swanny	Phrs. In a hopeless situation. Meaning the same as 'up shit creek'.
up the wrong 'un	Phrs. Up the anus. From up the wrong one.
uptight	Adj. Frigid, conventional, stressed. [Orig. U.S.] {Informal}
up your bum!	Exclam. 1. An angry and dismissive exclamation. 2. Cheers!
up your clunges!	Exclam. A dismissive and angry exclamation. See 'clunge'.
up yours!	Exclam. Exclamation of anger or defiance, usually directed at someone.
Uri (Geller)	Noun. Stella Artois, a popular brand of lager. Rhyming slang on Stella. Uri Geller, famous for his involvement in scientifically unexplained phenomena, such as bending metal spoons by the use of the power of mind.
use one's loaf	Vrb phrs. To think, to use one's ingenuity, to use one's head. Loaf (of bread) being rhyming slang for head.
use one's noggin	Vrb phrs. Meaning the same as 'use one's loaf'.