An impressionable/obnoxious teen snowboarder, skier, skater, etc... who has bought into Mountain Dew's marketing campaign that you have to loud obnoxious and "in your face" to be cool.
Dude, I don't hate snowboarders, it's just the the Mountain Douchebags I can't stand.
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?"