Dictionary.net

(Or "daughter board", "daughtercard", "daughtercard") A printed circuit board that connects to themotherboard. The daughterboard is typically smaller thanthe motherboard.A daughterdboard often adds to or supports the main functionsof the motherboard, unlike an expansion card whichprovides some new function. For example, a post-releasehardware modification might be released as a daughterboard forsoldering onto the motherboard.