when a couple has been dating for a week and the girl finds it necessary to celebrate. however her boyfriend doesn't remember so he gets himself into some deep shit.
Sarah: It's our weekiversary! Here's a new cellphone case!
Neil: Our what?
Sarah: we have been going out for a week! it's our weekiversary! i thought you cared about me!
Neil: Oh shit
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?"