A 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.
"piggyback board." YourDictionary, n.d. Web. 15 August 2018. <http://www.yourdictionary.com/piggyback-board>.
piggyback board. (n.d.). Retrieved August 15th, 2018, from http://www.yourdictionary.com/piggyback-board