1. To weaken or damage the power, credibility, or effectiveness of someone in a position of authority
The leaked documents undermine the authority of the government.
Os documentos vazados minam a autoridade do governo.
2. To gradually reduce someone's respect or influence in a position of leadership
Constantly disagreeing with your boss in public can undermine their authority.
Discordar constantemente do seu chefe em público pode minar sua autoridade.