The projecting part of the occipital bone at the base of the skull.
- ‘In these cases, the inion may be greatly enlarged.’
- ‘There is a slight occipital bunning and a very robust nuchal plane, inion, and mastoid/supramastoid region.’
- ‘For instance, bone thickness at inion averages 10.3 mm for A. afarensis and 12.8 mm for A. africanus.’
Early 19th century: from Greek, literally nape of the neck.