ˈkäksiks noun
( plural coccy·ges ˈkäksəˌjēz, käkˈsī(ˌ)j- ; also coccyxes ˈkäksiksə̇z)
Etymology: New Latin (Latin, cuckoo), from Greek kokkyx cuckoo, coccyx; from its resemblance to a cuckoo's beak — more at cuckoo
1. : the end of the vertebral column beyond the sacrum in man and certain other primates comprising usually four small vertebrae that are more or less completely fused in the adult and represent a vestigial tail
2. : a bone in vertebrates (as birds) corresponding to the primate coccyx ; sometimes : urostyle