plenipotentiary

This term is highly formal and primarily restricted to diplomatic, legal, or governmental contexts. It carries a connotation of absolute trust and high-level authorization, distinguishing the holder from a standard envoy or representative who might only carry a specific, limited mandate.

When used as an adjective, it typically modifies nouns like powers, authority, or credentials. As a noun, it refers to the individual holding that status. Because of its specialized nature, using it in casual conversation would be perceived as overly stiff or archaic.