Her slip 'peeked out' from beneath her skirt. [=a small part of her slip could be seen beneath her skirt]
We saw a 'sneak peek' [=a brief showing] of the movie that will be released next month.
They tried to 'sneak a peek' at the actors getting ready behind the curtain.
(..) who's embarrassing. What a phony. - But your dad's actually kind of cute. - - Shut up! - Come on. Like you've never sneaked a peek at him in his underwear? I bet he's got a big dick. I would. I would suck your dad's big fat dick, and then I'd fuck him until his eyes rolled back in his head. (..)1999 American Beauty