Source : Webster's Revised Unabridged Dictionary (1913)

Obelion \O*be"li*on\, n. [NL., from Gr. ? a spit.] (Anat.)
   The region of the skull between the two parietal foramina
   where the closure of the sagittal suture usually begins.

Source : WordNet®

obelion
     n : the craniometric point on the sagittal suture near the
         lamboid suture