Bone, coccygeal: The small tail-like bone at the bottom of the spine very near to the anus. The coccyx is made up of 3-5 rudimentary vertebrae. It is the lowest part of the spinal column. The word 'coccygeal' comes from the Greek 'kokkyx' meaning 'cuckoo bird.' It got this name because it was thought to look like the bill of the cuckoo.