A splinter in the ass,usually done while moving from a sitting position on wood or wood-like materials. A splass is very irritating and will hurt if rubbed against.
Me:Today i was trying to scootch over on the bleachers during gym and in the process, I GOT A SPLASS!
Them:A what?!
Me:A SPLINTER IN MY ASS!!!
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?"