1) A bum troll is a medical condition by which the affected person becomes aroused by pulling on the anal hair until it stands straight making the shape of a trolls hair.
2) A bum or homeless person with troll like hair.
1) Man I walked in on your Grandma taking a wicked New Jersey last night and she was bum trolling out of control. Multi-talented...nice!
2) Person A: Dude that bum troll keeps trying to sniff my fingers...
Person B: Man just let him! Bum trolls are people too.