A guy you mess around with when you hang out with him for no apparent reasion. You do this even though you know better, it happens almost everytime you hang out. This is how someone becomes a Mansteris. These can be good things or bad things. Mansteris(s) can become very negitive people in your life and an object your friends will use to make fun of. You and your mansteris(s) activities usually take place in random places when you don't think your friends are looking.
(1)Hey Rebecca, there goes your mansteris, boR.
(2)Omg! she made out with her mansteris in the woods at his party!?