A phrase describing a Vietnamese person (usually male) who takes on the characteristics of black people. A conjunction of the words brother (slang for how black people refer to each other) and do mai (a cuss word in Vietnamese which literally means "fuck you").
Similar to the word wangsta which describes a white person (usually male) taking on the characteristics of black people and is a derivative of the words wank (a derogatory word for white people) and gangster.
Conversation between two Vietnamese males:
What's up bro mai!
What up dawg! What's crackin'?