a moment of non-discretion. acting out in an irrational manner, acting suddenly "crazy" then becoming suddenly normal again.
"sorry dog i didn't mean to kick you in the face i was chapellin"
sorry for wiping my muddy feet on your couch dog, i was chapellin for a minute"
"tiffany kiessler seemed normal at first, but then she started chapellin now it clear she's a crazy beyyyyaaatch"