Pineal adj. Of or pertaining to a pine cone; resembling a pine cone. 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.