Source : Webster's Revised Unabridged Dictionary (1913)

Nunc dimittis \Nunc" di*mit"tis\ [L. nunc now + dimittis thou
   lettest depart.] (Eccl.)
   The song of Simeon (--Luke ii. 29-32), used in the ritual of
   many churches. It begins with these words in the Vulgate.

Source : WordNet®

Nunc dimittis
     n : the prayer of Simeon (Luke 2:29-32) [syn: {Canticle of
         Simeon}]