Definition of "occiput"

And then came Turbor, who sat quietly and unemotionally through the fifteen minute process, and Munn, who jerked at the first touch of the electrodes, and then spent the session rolling his eyes as though he wished he could turn them backwards and watch through a hole in his occiput.

1953, Isaac Asimov, “9: The Conspirators”, in Second Foundation (Foundation Series), Panther Books Ltd, Part II: Search by the Foundation, page 95

He wore a large white cotton Nubian shirt, trimmed with red pompons, and shaved his head, except for one lock at the occiput ‘by which Mohammed lifts you up on Judgement Day’.

2002, Alain de Botton, The Art of Travel, published 2008