The act of taking your ballsack and penis in your hand and twisting them up-side down to make it look like a fly's face.
Try The Fly's Eyes infront of the mirror first, once you have perfected it do it to people who will and wont appreciate it, the people who don't will make the people who do laugh... Workmates, girlfriends, her family!
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?"