b.boy is the slang term for breakdancer.
b boy is the word used to describe male breakdancers and b girl for females.
clothing is a usual indicator as to wether someone is a b boy/b girl but not always as it is a sport that people from many groups are into eg chavs punks joining together in the love of hihop/rap associated dancing.
at times they will be subject to a minimal degree of mockin
mainly by those who wish they could dance or becouse they look different.
(friend one) yo man, you see that show last night?
(friend two) yea that b.boy is the bomb
(friend one) yea but they totay look like wannabe gangstas
(friend two) shut up you jelouse prick