Source : Webster's Revised Unabridged Dictionary (1913)

Internuncio \In`ter*nun"ci*o\, n.; pl. {Internuncios}. [L.
   internuntius; inter between + nuntius, nuncius, messenger:
   cf. It. internunzio. See {Nuncio}.]
   1. A messenger between two parties. --Johnson.

   2. A representative, or charg['e] d'affaires, of the pope at
      a foreign court or seat of government, ranking next below
      a nuncio.

   Note: This title was formerly given also to the Austrian
         envoy at Constantinople.

Source : WordNet®

internuncio
     n : (Roman Catholic Church) a diplomatic representative of the
         Pope ranking below a nuncio