adamantine

/ˌædəˈmæntin/
adjective
  1. Extremely hard and impossible to break, cut, or scratch.
    • The scientist searched for an adamantine material to build the spacecraft's hull.
    • Her adamantine will helped her overcome every obstacle in her path.
    • The ancient sword was made of an adamantine metal that never dulled.
  2. Firm and unyielding in purpose or opinion; stubbornly determined.
    • She was adamantine about following the rules, even when no one was watching.
    • His adamantine refusal to compromise ended the negotiations.
    • Despite the protests, the mayor remained adamantine in her decision to close the park.
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