Nuncio
/ˈnʌnsiəʊ/
Definition 1 of 1
Pro Tip 1/3Religious Diplomacy
Nuncio is specific to Vatican diplomacy, not any ordinary ambassador. 
The nuncio worked closely with the local clergy to improve relations.
Pro Tip 2/3Papal Association
Often linked with the Pope, a nuncio is a key liaison for the Vatican state. 
The papal nuncio conveyed the Pope's message to the congregation.
Pro Tip 3/3Formal Address
Use 'nuncio' in formal contexts when referring to this high-level position. 
The nuncio received guests at the official state dinner.