noun: A situation that unexpectedly turns into an orgy where every bodily fluid is witnessed and sexual acts are performed as if the participants were playing sex dice and twister at the same time.
adj: unexpectedly and disturbingly sexual
Friend1: "Hey, sorry I couldn't make it to your movie night last night, how did it go?"
Friend2: "It was a real Urban Dictionary. I saw what I swear was santorum oozing from Jimmy's ass, but I couldn't tell because I got angry pirated before the previews even finished."
The biology class became increasingly Urban Dictionary as an orgy built up around the two kids who were munging with the pre-dissected fetal pigs.