Usually these are men who stalk younger women, go to parties they are too old for, or date/have sexual relations with their therapists/garbage women/mutual friends.
Marti: You're such a creeper.
Person B: totally, look at her percision!
2. A person who checks out your profile all the time to seek/gather information about a certain person. (Spying)
3. An older guy hitting on younger girls.
"Eww, i know, He's such a creeper!!"