used primarily in Wales, refers to a guy that thinks he is very good at everything but in reality is average at best. Constantly trying to show off and often exagerates/creates stories. Can also be used to refer to someone who thinks they are a lot 'cooler' than they are.
"I'm really good on the guitar, my band supported the Foo Fighters" "Shut up Das Butt"
"He claims to be a fantastic cricketer, but he's a Das Butt"
"I was the coolest guy in my school" "yeah right Das Butt you used to get bullied all the time!"
"Das Butt" is used in episode 67 of The Simpsons to describe a pornographic movie. The title of the movie is making reference to "Das Boot," a famous German submarine movie from 1981.
Hey, did you see Das Butt?