When you don't wipe your ass good enough and it starts to get itchy and or bother you in some way
"Dude, McDonalds didn't have any toilet paper so I had to wait till I got home and I had a bad case of bum disease"
by KKK is Bae June 11, 2016
One butt-cheek with an abnormal size and shape. The cause is from petting Giraffe tongues. Another cause is eating pretzel and cherrios at the same time. Side affects of Bum Disease are excrutiating pain. Feeeling an overwhelming attractivness to Mr.Collins. There is only two ways to cure this unfathomable disease, you must look pictures of sexy nerds and Mr. Darcy. from Pride and Prejudice .
Willis didn't go to school because he had Bum Disease.
by Fredwardmoo February 03, 2009