Stoned on mj such that the smile you smiled when you
smoked up is still there plastered all over your face an hour later because you neglected to unsmile or were too lazy, once the smile was there, to remove it. Comes from smoking good shit, or really
bad shit -- depending on your definition: ergo "shitfaced". From this perspective (regional usage, perhaps) it has nothing to do with alcohol. (i.e.
No shit, Sherlock.)
"Wipe that silly grin off thy face, thou
shitfaced bastard...
dost thou want thy boss to know thou art stoned?"
"Man, you are shitfaced... from ear to ear."
"Hey you shit-faced ex-pot-virgin, welcome to the
smile high club!"