A person who not nesessarily stalks other people, but gives you the creeps and might do awkward things. This person does not have to be a stranger either. You can know them well, but is not someone you want to associate with.
Girl One: Wow, Leon is such a creeper. He's sitting all by himself in the loner seat at the movies.
Girl Two: Yeah, what kind of person sees Reno 911 by themselves, anyway? What a creeper.