(1) The act of splattering the porcelain (or any other object)with non-solid stools after a particularly heavy drinking session, or after having been anally mounted by a man who has eaten a lot of celery ;)
(2) Can be used in context pertaining to verbal diarrhoea.
(1) "Mother? Fetch the mop. I'm about to shibbledash the cat..."
(2) "You're talking shibbledash, Hawking, and stop dribbling."