Brought into play when one person rejects the romantic advances of another, so as to remind the other that attraction (or lack thereof) is a state resulting from complex and immutable socio- psycho- and biochemical phenomena, and not in fact a value judgment on which offense should be taken.
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?"