The Collaborative International Dictionary of English v.0.48:

Internuncio \In`ter*nun"ci*o\, n.; pl. Internuncios. [L.
   internuntius; inter between + nuntius, nuncius, messenger:
   cf. It. internunzio. See Nuncio.]
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   1. A messenger between two parties. --Johnson.
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   2. A representative, or charg['e] d'affaires, of the pope at
      a foreign court or seat of government, ranking next below
      a nuncio.
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   Note: This title was formerly given also to the Austrian
         envoy at Constantinople.
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