plenipotentiary
Concise Oxford English Dictionary © 2008 Oxford University Press:
plenipotentiary /ˌplɛnɪpəˈtɛnʃ(ə)ri/
▶noun (pl. plenipotentiaries) a person, especially a diplomat, who is invested with the full power of independent action on behalf of their government. ▶adjective having full power to take independent action.
■ (of power) absolute.
– origin C17: from med. L. plenipotentiarius, from plenus ‘full’ + potentia ‘power’.
'plenipotentiary' also found in these Oxford entries:

