Want to know what "book google" or "cubicle coma" means? Not sure about a particular piece of slang you heard on TV? Urban Dictionary is your source for weird, occasionally obscene, and completely hilarious definitions of up-to-the-minute phrases and words. Like Wikipedia it is written by the community; however, anyone can submit a definition for an entry, and then viewers vote it up or down depending on their opinion of its correctness.
I've lost hours on Urban Dictionary following weird slang chains and horrifying definitions, so user beware. If you don't mind being amused and insulted by turns, though, I can definitely recommend it as a valuable pop-culture reference and resource!
(As always, I'm unaffiliated with anything I recommend!)