n :  either of two prominences on the occipital bone:  a  :  a prominence on the outer surface of the occipital bone midway between the upper border and the foramen magnum that with the external occipital crest gives attachment to the ligamentum nuchae - called also external occipital protuberance , inion   b  :  a prominence similarly situated on the inner surface of the occipital bone - called also internal occipital protuberance  .
 
 
 
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