Source : Webster's Revised Unabridged Dictionary (1913)

Magnificat \Mag*nif"i*cat\, n. [L., it magnifies.]
   The song of the Virgin Mary, --Luke i. 46; -- so called
   because it commences with this word in the Vulgate.

Source : WordNet®

Magnificat
     n : (Luke) the canticle of the Virgin Mary (from Luke 1:46
         beginning `Magnificat anima mea Dominum')