Definitions
1.nounAn imaginary rock or mineral of impenetrable hardness; a name given to the diamond and other substances of extreme hardness.
2.nounAn embodiment of impregnable hardness.
3.nounA lodestone.
4.adjective(said of people and their conviction) Firm; unshakeable; unyielding; determined.
5.adjective(of an object) Very difficult to break, pierce, or cut.