Hobbs Ass
Usually when a male (but can be a female I guess)is wearing boxers on a hot day, and the sweat from his ass saturates the boxers to the point that it makes it extremely uncomfortable to walk normally. It causes the individual to engage in a form of hobbling, hence "hobbs" ass.
"Dude, I had to run a mile wearing jeans and boxers and now I got the worse case of Hobbs Ass.