Source : Webster's Revised Unabridged Dictionary (1913)

Cranium \Cra"ni*um\ (kr?"n?-?m), n.; pl. E. {Craniums} (-?mz),
   L. {Crania} (-?). [NL., fr. Gr. ????; akin to ??? head.]
   The skull of an animal; especially, that part of the skull,
   either cartilaginous or bony, which immediately incloses the
   brain; the brain case or brainpan. See {Skull}.

Source : WordNet®

cranium
     n : the part of the skull that encloses the brain [syn: {braincase},
          {brainpan}]
     [also: {crania} (pl)]