[ 'pɪnɪəl , 'pʌɪ- ]
(also pineal body )
■ noun a pea-sized conical mass of tissue behind the third ventricle of the brain, secreting a hormone-like substance in some mammals.
Origin
C17: from Fr. pinéal , from L. pinea 'pine cone' (with ref. to the shape of the gland).