nuncio:
(also ‘papal nuncio‘, ‘Apostolic nuncio‘; plural: ‘nuncios‘; pronunciation: the letters ‘nun’ rhyme with the word “nun” — for the right pronunciation of this word, please click here)
a high official/diplomatic representative from the Pope’s office with a status of an ambassador,
Before His Holiness the Pope pays a visit to any country, the nuncio will arrive and discuss the necessary arrangements with the heads of that state.
The Pope depends mostly on his nuncios around the world in some important administrative matters, including finding suitable archbishops and bishops, arrangements for his visit and stay in the countries they are in charge, and so on.
As with every thing else, there are good and bad nuncios in the Roman Catholic Church, and though they are above the ranks of bishops, priests and other Church officials, some nuncios are also sued on charges of child molestation and sexual harassment!

