adamant

This term describes a level of firmness that borders on inflexibility. It suggests a psychological state of being unyielding, where the person has reached a final decision and is completely closed to further negotiation or influence. It carries a stronger, more resolute tone than simply being stubborn, often implying a sense of conviction or principle. In professional or formal settings, it is used to signal a non-negotiable boundary. While it can be perceived as positive when describing strength of character, it can also imply a lack of openness or a refusal to compromise in a collaborative environment.