a website you visit when myspace is being a biotch and your to lazy to call a friend over or jerk off.
you can also define the stupid slang terms your friends have invented, give a dirty definition to everything from apple to zebra, or plainly just bitch about your haters.
UD Noob: "oo interesting! no one has defined rubber band yet!"
*typing in urban dictionary definition box*
Rubber band: sticking your head in someones private area and yelling out applesauce repeatedly.