1) Back of the skull 2) Bulge at rear of skull 3) Bulge at the back of the head 4) Bulging rear of skull 5) Bulging rear of the skull 6) Cranial bump 7) Craniometric point 8) Occipital point 9) Occipital protuberance 10) Part of the skull 11) Skull bone 12) Skull bulge 13) Skull bump 14) Skull part 
The inion is the most prominent projection of the occipital bone at the posterioinferior (lower rear) part of the skull. The ligamentum nuchae and trapezius muscle attach to it. The term external occipital protuberance (protuberantia occipitalis externa) is sometimes used as a synonym, but more precisely the term `inion` refers to the highest po.....
• (n.) The external occipital protuberance of the skull.
(in´e-on) the external occipital protuberance. adj., in´ial., adj.
In'i·on noun [ New Latin , from Greek 
Type: Term Pronunciation: in′ē-on Definitions: 1. A point located on the external occipital protuberance at the intersection of the midline with a line drawn tangent to the uppermost convexity of the right and left superior nuchal lines.
[n] - the craniometric point that is the most prominent point at the back of the head (at the occipital protuberance)
noun the craniometric point that is the most prominent point at the back of the head (at the occipital protuberance)
a point at the external occipital protuberance of the skull.