The Collaborative International Dictionary of English v.0.48:

Cephalic \Ce*phal"ic\, a. [L. cephalicus, Gr. ?, fr. kefalh`
   head: cf. F. c['e]phalique.] (Anat.)
   Of or pertaining to the head. See the Note under Anterior.
   [1913 Webster]

   Cephalic index (Anat.), the ratio of the breadth of the
      cranium to the length, which is taken as the standard, and
      equal to 100; the breadth index.

   Cephalic vein, a large vein running from the back of the
      head alond the arm; -- so named because the ancients used
      to open it for disorders of the head. --Dunglison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cephalic index
    n 1: ratio (in percent) of the maximum breadth to the maximum
         length of a skull [syn: cephalic index, breadth index,
         cranial index]