Pink Finger a.k.a. 'Taggers Thumb' is a fictional condition caused by a rare cancer of the spine which causses your digits turn un-natural colours. In reality it is a result of too much stencil-bombing.
1. Ant: Mum, can I have the day off school, my pink finger's flared up again?
2. Tom: Ant, move you hand or you'll get pink finger.
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?"