anything you are trying to explain to someone and can't remember the name of
you ask your friend to pass you a certain tool and you can't remember the name of so you say to your friend you know the whodiddy! its the new generation for the saying thingy majiggy
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?"