1. A rude and threatening panhandler that begs for money, but at the same time demands it.
2. A drug addict or crack head that is still in good health and begs for money with the threat of violence.
3. Commonly found on college campus's in the United States, bully bums run in packs and take money from freshman students and weaklings.
weakling: There are a bunch of bully bums up there. Lets cut through the alley.
Ford: Fuck them bully bums. I'm gonna bash their brains in with a brick.