obvious; no kidding, sherlock!, or are you kidding me?
Erica: Do you think Taylor Laurtner is sexy?
Madison: Duh! He's like, the hottest dude in Hollywood!
A very beautiful word used to describe something very obvious
Kendall: do you like dogs
Sally: duh shitty
Duh = Thats Obvious, you moron!
dude 1: Hey bro, have you beat the Ender Dragon in minecraft yet?
dude 2: well, duh!