to be put on notice; to be called out. to be served is an open invitation to serve back. unless you can serve back in equal or better fashion, then you got owned and have been bumped in ranking. to be served originates from being served with documents that you need to appear in court.
Me and my b-boy crew were pop-lockin and chillin, then this other crew came up and tried to serve us, but we had better moves, so those bitches got served back and owned.