A name given to guy friends who are funny and generally great people. It makes them sound like some sort of prostitute, so consequently think it makes them sound greater. You like the guy for who they are, and they are a true friend to you. You can trust them. Usually a name given to them by a girl, as from a fellow guy, it could sound rather strange...
"Yo, my man bitch!"
"Would you like to be my man bitch, because you are cool!?"
"He's my man bitch, get away from him or I'll bite you!"