Acronym for Broke A** Motherf*cker. Used as a noun and a verb. As a noun, it describes a person who is cheap or actually has no money. As a verb, it describes the act of borrowing something without asking.
Noun: Does Kramer have any money for the pizza? No, he's a BAM this week.
Verb: I came home from a night out, and realized that someone had bamed the pizza I had in the fridge!