Creepy is not paying attention to the subtle social signals that someone gives you to back off a bit.
A man is creepy when he doesn’t meet you halfway, or even pay attention to what you might want and just takes you in like you owe him or like you are an object.
Most girls (or people in general) don’t like to straight-up tell you “Go away,” but they’ll send a number of signals to indicate that they’re uncomfortable or don’t want to talk to you.