When your nipples can be seen poking through clothing, often because of cold weather, sexual arousal, or particular types of clothing. Many women wearing bathing suits and sports bras tend to have a problem with this because of thin coverage, feeling uncomfortable at the prominent exposure of their body.
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?"