Itching and chaffing in the grundle and butt crack region associated with wearing damp swim trunks. Discomfort is exaggerated with the addition of sand and/or miscellaneous detritus caught in old-school swim trunk ball-netting.
Typically associated with male-oriented swimwear although not exclusive to the gender. The female persuasion has far-worse potential for foul ramifications.
"I've got rupadupalus so bad it feels my balls are being slapped-about by an angry dwarf with 80 grit sandpaper!"