Piggyback board | Article about piggyback board by The Free Dictionary
piggyback board[′pig·ē‚bak ‚bȯrd]
A small printed circuit board that is mounted on a larger board to provide additional circuitry.
piggyback boardA small printed circuit board that plugs into another circuit board in order to enhance its capabilities. It does not plug into the motherboard, but would plug into the boards that plug into the motherboard.