Plenipotentiary

Part of speech: noun (n.)

A person invested with full power to transact any business; especially, an ambassador or envoy to a foreign court, with full power to negotiate a treaty, or to transact other business.

Part of speech: adjective (a.)

Containing or conferring full power; invested with full power; as, plenipotentiary license; plenipotentiary ministers. Howell.