Made solely from plain white bread and one slice of processed cheese, it is typically a sandwich eaten by someone who has hit rock bottom. The only additional ingredient allowed beyond bread and processed cheese is hot sauce; however, this changes the title to "spicy bum sandwich". Other abbreviations include: Hot bum sandwich (microwaved), Toasted bum sandwich (toasted white bread) or the famous one slice folded over version "the bum foldwich".
"Whats for lunch asshole?" "Bum sandwiches and liquor. Then I'm going to the dump to shoot rats."