Source : Webster's Revised Unabridged Dictionary (1913)

Prosencephalon \Pros`en*ceph"a*lon\, n. [NL., fr. Gr. ? toward,
   near to + E. encephalon.] [Sometimes abbreviated to proen.]
   (Anat.)
   (a) The anterior segment of the brain, including the cerebrum
       and olfactory lobes; the forebrain.
   (b) The cerebrum. --Huxley.

Source : WordNet®

prosencephalon
     n : the anterior portion of the brain; the part of the brain
         that develops from the anterior part of the neural tube
         [syn: {forebrain}]
     [also: {prosencephala} (pl)]