Source : Webster's Revised Unabridged Dictionary (1913)

Annunciation \An*nun`ci*a"tion\ (?; 277), n. [L. annuntiatio:
   cf. F. annonciation.]
   1. The act of announcing; announcement; proclamation; as, the
      annunciation of peace.

   2. (Eccl.)
      (a) The announcement of the incarnation, made by the angel
          Gabriel to the Virgin Mary.
      (b) The festival celebrated (March 25th) by the Church of
          England, of Rome, etc., in memory of the angel's
          announcement, on that day; Lady Day.

Source : WordNet®

Annunciation
     n 1: a festival commemorating the announcement of the Incarnation
          by the angel Gabriel to the Virgin Mary; a quarter day
          in England, Wales, and Ireland [syn: {Lady Day}, {Annunciation
          Day}, {March 25}]
     2: (Christianity) the announcement to the Virgin Mary by the
        angel Gabriel of the incarnation of Christ
     3: a formal public statement; "the government made an
        announcement about changes in the drug war"; "a
        declaration of independence" [syn: {announcement}, {proclamation},
         {declaration}]