This is the 15133rd most frequent Russian word.
полномочный
Authorized; empowered.
The word 'полномочный' here describes someone having full power or authority to act as a representative.
Он был назначен полномочным представителем компании в регионе.
He was appointed as the authorized representative of the company in the region.
In this context, 'полномочной' is used to signify a mission endowed with full authorization.
Посол прибыл с полномочной миссией от своего правительства.
The ambassador arrived with a plenipotentiary mission from his government.
Here, 'полномочный' qualifies a body or entity as having the authority to make decisions.