- utterly unyielding in attitude or opinion in spite of all appeals, urgings, etc.
- too hard to cut, break, or pierce.
- any impenetrably or unyieldingly hard substance.
- a legendary stone of impenetrable hardness, formerly sometimes identified with the diamond.
- unshakable in purpose, determination, or opinion; unyielding
- a less common word for adamantine (def. 1)
- any extremely hard or apparently unbreakable substance
- a legendary stone said to be impenetrable, often identified with the diamond or loadstone
