run a piece on a girl

To run a piece on a girl can mean one of two things: to have sex with a girl in exchange for money, drugs, or whatever they decide to exchange.

To run piece on a girl can also mean: to con or steal from her in plain sight without her knowledge, especially if she is in debt to someone

I'll hit you up later but first I have to run a piece on a girl who needs some Boi or tonight, but she don't have any money.