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

ice	Noun. Diamonds or more generally jewellery. [Orig. U.S.]
ick	Noun. A distasteful substance. Probably derived from the adjective icky.
ickle	Adj. Small, little. A mock juvenile shortening of the word 'lickle'. Cf. 'lickle'.
icky	Adj. Gooey or sticky, usually denoting unpleasantly so. {Informal}
iffy	Adj. Unsound, incorrect, improbable, suspicious.
ignorant	Adj. Not polite, disrespectful, rude. {Informal}
iky	Adj. Frugle, stingy. [Dundee use]
I'll be buggered!	Exclam. An exclamation of surprise.
I'll be buggered if...	Exclam. There's no way. E.g."I'll be buggered if I'm going to help him after what he said about my sister."
I'll go to the foot of our stairs!	Exclam. An exclamation of surprise. [Lancs/Yorks use]
in a bit!	Exclam. Goodbye! See you later!
in bits	Adj. Mentally confused. E.g."It's no wonder he's in bits, he's had two tabs of acid, four grams of coke and smoked an ounce of draw."
in bulk	Phrs. Laughing. E.g."Sarah was in bulk all the way through the film." [Merseyside use]
in cahoots with	Phrs. In league with, colluding.
in deep shit	Phrs. In big trouble.
indie	Noun. A type of guitar orientated music derived from 'punk'. Indie has generated its own fashions as with most youth music. Originally an abb. of independent, being a record label not affiliated to a major label such as Sony or EMI.
indie-kid	Noun. A person who is keen on 'Indie' music and wears its fashions.
(the) information superhighway	Noun. The rather impassioned and premature title given to the World Wide Web. This expression has already lost popularity and rarely used within the Internet community. [Late 1980s]
innie	Noun. A navel or belly button that doesn't protrude, as is the case with the majority. Cf. 'outtie'.
innit!	Exclam. A questioning statement. E.g."That's got to be the best goal ever, innit!"
inside	Adj. In prison. E.g."I'm a bit out of touch, having being inside for the last two years"
inside job	Noun. A crime committed against an organisation or property, by a affiliated person. {Informal}
in shtook	Adj. In trouble. Has various spellings such as in shtuk/stook/schtuk/schtook which has been suggested comes from Yiddish.
in the altogether	Phrs. Naked. E.g."She walked in on Mike, screamed, and ran downstairs crying. Mind you he was in the altogether."
in the buff	Phrs. Naked.
in the club	Phrs. Pregnant. A contraction of in the pudding club.
in the doghouse	Phrs. Out of favour. Said of a person. E.g."My dad's in the doghouse after getting drunk last night."
in the niff	Phrs. Naked. [Yorkshire use]
in the nuddy	Phrs. Naked.
in the scud	Phrs. Naked. See 'scud mag'. [Mainly Scottish use]
into	Prep. Interest, like what's your bag ?. E.g."What are you into?"
irie *	Adj. Nice, great, fine. Exclam. Expressing approval or good wishes. Also as a greeting. * [Orig. Jamaican. Mainly Black/Jamaican use]
iron	Noun. A homosexual. Rhyming slang on iron hoof meaning 'poof'
I should cocoa!	Exclam. I should say so! A London expression used with irony and often jocularly by those from outside the city. The cocoa or coco is rhyming slang for say so.
item	Noun. A couple in a steady relationship.
ivories	Noun. Teeth.