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15.
(Adj.): Synonym for the slang use of "crazy"; wild, entertaining; of a nature that is indescribably cutting-edge
"That Cirque du Soleil show was absolutely crack!"

"Yah. It was pretty crazy. Now Miles Davis's "Bitches Brew"--this jazz is crack, all over the place.
by Nietzschehope July 10, 2008
 
16.
something really good, pretty much addicting
reasonable doubt is straight crack, yo.
by yoner September 08, 2007
 
17.
Z-Ro's new album.
Shit i just bought Z-ro's new album Crack that hoe jammin like a muthafucka.
by cracker88 October 10, 2008
 
18.
Use this word when describing something good or well-done.
Yo that new song is Crack!
by Cantave August 11, 2007
 
19.
a now obsolete adjective popular as a business buzzword among yuppies in the early eighties. It described a worker who was very smart and very fast-paced.

This meaning of "crack" was forced out by the drug, crack, in the mid-eighties. Sort of like you can't say "gay" to mean "happy" anymore.
That was a good move to hire him; he's crack.
by Dr. Heywood R. Floyd May 20, 2007
 
20.
crack cocain, a white drug substance that fucks you up.
crack... drywall dust... what's the difference?
by Vw4Life September 11, 2008
 
21.
Short for crack cocaine, usually a white powdered solid.

Also known as 'knowledge trees', among other things.
GUY 1: Lets go get some crack.
GUY 2: I LIVE FOR KNOWLEDGE TREES!!!
by Bobbick January 08, 2008