A low cost piece of transportation equipment e.g. Shopping cart, Wheelbarrow, Bike, Sled. Used by Bums (aka homeless people) to transport their only possesions with them. Mainly old cans, bottles, and any smelly old clothes they have with them. It is a very important piece of equipment for a bum and their livelyhoods depend on it.
That Bum has a phat Bum Mobile yo!
A highly mobile bum should have his own Bum Mobile.