One of the answers in a recent New York Times crossword, illin', has resulted in a great deal of comment on the internet. The New York Times crossword is a straight crossword, not cryptic, so that generally means that the clues should be straightforward. The clue for illin' was 'Wack, as in hip hop'.
Now, at this point in the story (which I read on the Guardian Crossword blog), I got lost, since I had never heard of the words 'slang' 'illin' (amended due to typo - thanks, John, for pointing it out) or 'wack' (except for wack used the Liverpudlian way). A reader had written in to the newspaper saying that wack and illin' were not the same thing. The paper's very eminent crossword editor, Will Shortz, replied that they were the same, illin' being hip-hop slang for 'bad' or 'uncool' and wack meaning 'worthless' (the full correspondence between the reader and Shortz can be read here). An article in the Gawker, which I linked to in the last sentence, too, says that the meaning of illin' is malleable -- it can mean wack, crazy or chilling.
The hip-hop slang adjective ill is in the OED -- it went in in 2006. It has two, completely opposite, definitions: a) "Aggressive, irrational, crazy; unpleasant, bad" and b) "Excellent, attractive; fashionable". Wack is in the OED, too; its original meaning (from the 1930s) was 'an eccentric or crazy person', then the meaning 'bad, harmful; unfashionable, boring' went in in the 1980s.
Here's the Guardian Crossword blog.