A young guy, typically driving a suped up or "tricked" out Civic or Lancer who also is usually behind the times from a fashion standpoint (i.e. lanyard hanging out of his pants that says "Go Army" from 4 years ago). For the most part, you can find a sit bitz also wearing a flat-brimmed hat tilted sideways. They also lean back in the driver's seat with their right hand on the steering wheel and their left hand on their mouth. They think they are so cool so that when you see them your first response is "shit, bitch." But they are so cool you simply say "sit, bitz" because they're too lazy to say the whole words. Typically, sit bitz's are talking about something that they think is cool.
"You man I had like 15 beers last night."
You would say to them, "Sit bitz."
Or, if you are proud of something, simply say "sit bitz"