The condition one gets when trying to not look high on marijuana. Most commonly seen on first time users. consists of opening eyes extremely wide, small smirks, jaw clenching and short usually one-worded answers followed by long rambling ones.
Mom: hey honey did you have a good time?
Mom: are you alright?
Mom: why are you smiling like that?
Kid: oh I was just thinking about this thing that happened, it was really funny, kyle fell, but he also fell and took down this old lady, but none of them were hurt, that wouldn't have been funny, that would have been really sad...(Etc.)
Mom: you're high.
Kid: no I'm not.
Mom: yes you are you got Stoney Face, just go watch cartoons.