Definition: A weird or disturbing person; an annoying person.
1) Some creep was bothering me last night at the party.
2) I hate it when my little brother follows us around. He's such a creep!
Etymology: Small creatures such as spiders and rats 'creep around', which means that they move with their bodies close to the ground. Many people are afraid of such creatures and avoid them. As slang, a 'creep' is someone who reminds you of a spider or rat and makes you want to avoid him.