nuchal line

: any of several ridges on the outside of the skull: as

a : one on each side that extends laterally in a curve from the external occipital protuberance to the mastoid process of the temporal bone

— called also superior nuchal line

b : occipital crest sense a

c : one on each side that extends laterally from the middle of the external occipital crest below and roughly parallel to the superior nuchal line

— called also inferior nuchal line