A website where people go to rant about things that they have no clue whatsoever about. Here's the way it works most of the time: Person stumbles upon UrbanDictionary.com. Person becomes angered at others' definition, clicks it down. Person writes their own definition of the same word that they looked at, condescending everything that person said. Repeats process.
I just finished posting something on Urban Dictionary. I don't know what I'm talking about of course and I'm so biased that I suck at life.