Euphemisms

A few boys were beat boxing and banging on their desks.  I looked at them, obviously annoyed.

Me, deadpan: That's a dope beat.  
Boy: Yeah, we're awesome!
Me: Uh huh...
Boy: Dude, let's all beat.  Let's have a beat off!

I immediately whipped my head around and let out a huge surprised laugh.  The kid stopped and realized what he said. I buried my head in my hands and continued laughing until I cried.