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: Webster's Revised Unabridged Dictionary (1913)