The act of laying several highly-potent farts inside of a car just before someone you know is going to get in, leaving them with a surprise attack of fermented fart upon opening the door.
Bill, when I got back from the grocery store today, I left a PolishAssassin waiting in the car.. My girlfriend got in and threw up all over the dash!
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?"