to be constantly grining.usually from the affects of acid, LSD.
Man he's tripping so bad he got permagrin
a "permanent grin" which one can only achieve through being in a totally different dimension (usually through use of peyote, lsd, and is definitely popular with shrooms)
guy1: so herd everyone went trippin this weekend, how was it?
guy2: it was great, everyone was real chill, paul's dumbass had a stupid perma grin that he couldnt wipe off and he didnt say shit the whole time. Hes such a sleezebag.