A common exclamation used as a substitute for Holy Shit to describe an exiting, ridiculous or unbelievable event. It's a very popular amongst those who avoid cursing. It's similar to other curse word substitutes like Holy Cow or Holy Schnikes .
Holy Canoli did you see that one-handed touchdown catch to win the game?
An exclamation, when your numpty cousin john's kids are around and he doesn't want you swearing in front of them, but you just stubbed your toe so flipping hard and you gotta react in some way, but little timmy is two feet away and john is looking right at you so you have to say them that gets as close to the satisfaction of yelling "FUCK" really loudly after stubbing your toe but- ... what was i talking about?
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?"