tattered windsock

To render one's anus or vagina in a graphical state of distress, as a result of a particularly violent bowel movement or penetrative intercourse.
The description comes from the similar appearance to the ripped edges of a windsock (an item of metrological equipment used to establish wind speed/direction) as used at airports/flying schools, etc., which have become tattered as a result of excessive weather conditions.

"God, that curry last night was awesome - my arse puckered starrusty sheriff's badgechocolate tea towel holder this morning was like a tattered windsock"

"He was hung like a horse; my twat vadgegrowleryeti's welly looked like a tattered windsock afterwards"