It is a person who was usually sexually abused early in life (up to 15 years of age) who later becomes sexually dysfunctional in life. They often become sexually active with children or teenagers of either sex but tends to go with someone of the same sex.
It also means that the person is attracted sexually to an underage person but without sexual contact.
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"