The Collaborative International Dictionary of English v.0.48:

Pineal \Pi"ne*al\, a. [L. pinea the cone of a pine, from pineus
   of the pine, from pinus a pine: cf. F. pin['e]ale.]
   Of or pertaining to a pine cone; resembling a pine cone.
   [1913 Webster]

   Pineal gland (Anat.), a glandlike body in the roof of the
      third ventricle of the vertebrate brain; -- called also
      pineal body, epiphysis, conarium. In some animals it
      is connected with a rudimentary eye, the so-called pineal
      eye, and in other animals it is supposed to be the remnant
      of a dorsal median eye.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pineal gland
    n 1: a small endocrine gland in the brain; situated beneath the
         back part of the corpus callosum; secretes melatonin [syn:
         pineal gland, pineal body, epiphysis cerebri,
         epiphysis]