inion

The most prominent projecting point of the occipital bone at the base of the skull.

An onion. This pronunciation is shown, without the changed spelling, in the second extract.

In anatomy, a ridge of the occiput to which muscles of the nape are attached; now, specifically, the external occipital protuberance.

The external occipital protuberance of the skull.

A small protuberance on the external surface of the back of the skull near the neck; the external occipital protuberance.

the craniometric point that is the most prominent point at the back of the head (at the occipital protuberance)