The Collaborative International Dictionary of English v.0.48:

Nuncio \Nun"ci*o\, n.; pl. Nuncios. [It. nunzio, nuncio, fr.
   L. nuncius, nuntius, messenger; perh. akin to novus new, E.
   new, and thus, one who brings news. Cf. Announce.]
   [1913 Webster]
   1. A messenger. [Obs.] --Shak.
      [1913 Webster]

   2. The permanent official representative of the pope at a
      foreign court or seat of government. Distinguished from a
      legate a latere, whose mission is temporary in its nature,
      or for some special purpose. Nuncios are of higher rank
      than internuncios.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nuncio
    n 1: (Roman Catholic Church) a diplomatic representative of the
         Pope having ambassadorial status [syn: nuncio, papal
         nuncio]