'adamantine' definitions:

Consisting of or having the hardness of adamant

Having the hardness of a diamond

Impervious to pleas, persuasion, requests, reason; "he is adamant in his refusal to change his mind"; "Cynthia was inexorable; she would have none of him"- W.Churchill; "an intransigent conservative opposed to every liberal tendency" [syn: adamant, adamantine, inexorable, intransigent]