zygapophysis

In most tetrapods including the human, the vertebrae are connected with each other only via the centrum and the zygapophysis joints.

These stick out of an end of a vertebra to lock with a zygapophysis on the next vertebra, to make the backbone more stable.

The wide body of the axis had a deep gouge; the posterior zygapophysis had broken clean off, and the fracture plane went completely through the centrum of the bone.