After having a hefty poo (normally in someone else's toilet), standing up and turning round to inspect the damage but noticing you've left a rather nasty looking skidmark on the bowl. To irradicate the skidmark you forcefully urinate on it, eroding it into nothingness. A second flush is always necessary in order to remove any fragments.
Sylvain was distraught when he inspected the dump he'd just done in his girlfriend, Julia's toilet - there were more skidmarks than on an Indy 500 circuit! Fortunately Sylvain was a crafty chap and realised that a decent spot of Japanese Pressure Washing would remove all the carnage.