When your enthusiastic about something but have no idea what it is or why you should care. Basically when your bored into a braindrunk fart by your present company, then some grinning idiot looks at you so you have to respond with a proportionate enthusiasm, and this is what flops out.
Kevin: :D
You : ".........Billiant, yeahreally .....Billiant!"
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?"