Origin: 2014, Skype
hot·core or hot-core (hôt′kôr′, -kōr′, hŏt′-)
adj.
1. Being even more explicit than hard-core material in depicting or describing sexual activity: hotcore pornography.
2. A indescribable level of extreme: a hotcore sports fan, a hotcore gamer, a hotcore leader (e.g. Hitler)
"That new hotcore porn makes hardcore porn look like church sermon."
"Our understanding of science is not yet at levels that are hotcore enough to grasp dark matter and dark energy"
"Jesus would have been a hotcore deity had he not been stabbed to death"
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?"