(n.) A person or object that fails to turn up when it has been arranged to appear.
Adolf Hitler: Those jews were a no show for thier shower today.
Rommel: I guess they thought better never than late, eh?
Adolf Hitler: Yeah.
(n.) A person who signs up or talks about attending certain events, but never shows up.
Fred: Hey, where is Bob? I have his name here on the sign up sheet.
Lindsey: Man, that tool Bob never comes when he says he will. What a no show.