cortex

noun

1. the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum

   noun.body

   Synonyms cerebral cortex cerebral mantle pallium

   Source: WordNet 3.0

2. the tissue forming the outer layer of an organ or structure in plant or animal

   noun.body

   Antonyms medulla

   Source: WordNet 3.0

3. the tissue that surrounds the lens nucleus

   noun.body

   Synonyms lens cortex

   Source: WordNet 3.0

4. Bark, as of a tree; hence, an outer covering.

   noun

   Source: webster1913