Source : Webster's Revised Unabridged Dictionary (1913)

Cortex \Cor"tex\ (k?r"t?ks), n.; pl. {Cortices} (-t?-s?z). [L.,
   bark. Cf. {Cork}.]
   1. Bark, as of a tree; hence, an outer covering.

   2. (Med.) Bark; rind; specifically, cinchona bark.

   3. (Anat.) The outer or superficial part of an organ; as, the
      cortex or gray exterior substance of the brain.

Source : WordNet®

cortices
     See {cortex}

cortex
     n 1: the layer of unmyelinated neurons (the gray matter) forming
          the cortex of the cerebrum [syn: {cerebral cortex}, {cerebral
          mantle}, {pallium}]
     2: the tissue forming the outer layer of an organ or structure
        in plant or animal [ant: {medulla}]
     [also: {cortices} (pl)]