Firm; unshakeable; unyielding; determined.
Very difficult to break, pierce, or cut.
An embodiment of impregnable hardness.
An imaginary rock or mineral of impenetrable hardness; a name given to the diamond and other substances of extreme hardness.
Not noble; ignoble; base.
Of a metal, being at the lower end of the electrochemical series, i.e. oxidising readily.
To make (someone or something) no longer noble