Someone who wears the same thing to school every single day. Usually a male with a broken backpack that doesn't zip up and only has one arm strap. A Bum must be a fan of the San Francisco 49ers and such a big fan to the point makes people hates the niners. A Bum gets picked on constantly, there are even official "Give a bum a deadleg day" "Beat a bum up day" etc. When a Bum is asked "What can Brown do for you?!" He must reply with "The real question is what can't brown do for you ;]"
Lastly, Not to be confused.
Aliens > Bums
Bum: (Walks in Late, Ipod headphones in ears, No one is sure if the Bum is sober)
Weight Training Class: "MR BUMMMMMMMMMMMMMMMMM!!!!"