PLENIPOTENTIARY

adj. authorized, qualified; has full authority, has power of attorney

n. ambassador, diplomat; official representative; delegate, messenger

The word plenipotentiary (from the Latin, plenus + potens, full + power) has two meanings.As a noun, it refers to a person who has "full powers". In particular, the term commonly refers to a diplomat who is fully authorised to represent their government as a prerogative (e.g. ambassador).As an adjective, plenipotentiary refers to that which confers "full powers".
See more at Wikipedia.org...

Noun
1. a diplomat who is fully authorized to represent his or her government
(hypernym) diplomat, diplomatist

(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.
  

(a.)
Containing or conferring full power; invested with full power; as, plenipotentiary license; plenipotentiary ministers.
  

Synonyms and related words:
absolute, all-powerful, almighty, ambassador, ambassadorial, ambassadress, apostolic delegate, attache, career diplomat, chancellor, charge, commercial attache, consul, consul general, consular, consular agent, diplomat, diplomatic, diplomatic agent, diplomatist, emissary, envoy, envoy extraordinary, foreign service officer, internuncio, legate, military attache, minister, minister plenipotentiary, minister resident, ministerial, nuncio, omnipotent, resident, secretary of legation, sovereign, supreme, unlimited, vice-consul, vice-legate