KATE AND SIDNEY PIE [noun]
Pronunciation Cait And Sid Nee Py
Meaning Steak and kidney pie.
Usage Eating? Throwing at people if you can't find any custard?
Origin Speverend Rooner. Or maybe his wife, given that women did all the cooking back then. My Dad uses it a lot though. For the first purpose, mind you.

KEN?
Pronunciation Ken.
Meaning You know?
Usage "That Begbie dude is one bad jungle cat, likesay, ken?"
Origin Spud of Trainspotting The Book.

KENDAL MINT CAKE! [exclamation / adjective]
Pronunciation Ken Dull Mint Cayk.
Meaning The commentary to use when something is not just mint, but very very mint.
Usage Probably fairly nutritional, but I've never eaten any.
Origin Kendal, Cumbria, England.

KENNETH
See No ta, Kenneth.

KEWELIEZ! [adjective / exclamation]
Pronunctiation Cue - el - eez!
Meaning Cool, in a teenybopper sense.
Usage "Like, omigawd, N Sync are soooooo keweliez!"
Origin Some aevil teenybopper, late 1998. The scary thing is, while the swans abducted it mockingly, we've had a lot more mileage out of it than the boppers ever got.

KEWR, THE [noun]
Pronunciation Cue-er, Thuh.
Meaning The Cure, 80s band of gawffeekness.
Usage Multiple, if you'll only give us the chance!
Origin Zed, May 1999. Strangely enough, Smill invented the same word at exactly the same time.