The Collaborative International Dictionary of English v.0.48:

Vatican \Vat"i*can\, n. [L. Vaticanus, mons, or collis,
   Vaticanus, the Vatican hill, in Rome, on the western bank of
   the Tiber: cf. F. Vatican, It. Vaticano.]
   A magnificent assemblage of buildings at Rome, near the
   church of St. Peter, including the pope's palace, a museum, a
   library, a famous chapel, etc.
   [1913 Webster]

   Note: The word is often used to indicate the papal authority.
         [1913 Webster]

   Thunders of the Vatican, the anathemas, or denunciations,
      of the pope.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Vatican
    n 1: the residence of the Catholic Pope in the Vatican City
         [syn: Vatican, Vatican Palace]