A piece of software, usually something lame that was installedby default with your OS, that takes over when your PC thinks you're not using it any more.
Some screensavers are cute, like Viking Kittens, and some have a purpose, like Make Love Not Spam, but most are just unimaginative lameness that installed by default with sWindles.
This is a sexual move inwich the girl is giving the guy oral and he gives her a facial, Then he takes a computer moniter and wacks her in the face multiple times.
Person 1: So how was that screen saver last night??