plen ‧ i ‧ po ‧ ten ‧ tia ‧ ry /ˌplenəpəˈtenʃ ə ri, ˌplenɪpəˈtenʃ ə ri $ -ʃieri/ BrE AmE noun ( plural plenipotentiaries ) [countable] formal technical
[ Date: 1600-1700 ; Language: Medieval Latin ; Origin: plenipotentiarius , from Latin plenus ( ⇨ ↑ plenty 3 ) + potens 'powerful' ]
someone who has full power to take action or make decisions, especially as a representative of their government in a foreign country
—plenipotentiary adjective