adamant adamant /ˈædəmənt/

adjective

1. () Impervious to pleas, persuasion, requests, reason  ( adamantine , intransigent , unbudgeable , adamant , inexorable )
   impervious to pleas, persuasion, requests, reason
    He is adamant in his refusal to change his mind
   he is adamant in his refusal to change his mind
    Cynthia was inexorable; she would have none of him
   Cynthia was inexorable; she would have none of him
    An intransigent conservative opposed to every liberal tendency
   an intransigent conservative opposed to every liberal tendency
   

noun

1. [Archaic] Very hard native crystalline carbon valued as a gem  ( adamant [Archaic] , diamond )
   very hard native crystalline carbon valued as a gem