椎骨

椎骨	zhuī gǔ	vertebra
椎	chuí	hammer; mallet (variant of 槌) / to hammer; to bludgeon (variant of 捶)
椎	zhuī	(bound form) vertebra
骨	gū	used in 骨碌碌 / used in 骨碌
骨	gǔ	bone