Synonyms and related words :
adamantness, dourness, firmness, flintiness, grimness, hard-bittenness, hard-nosedness, immovability, immutability, implacability, impliability, inelasticity, inexorability, inflexibility, intransigeance, intransigency, intransigentism, irreconcilability, obduracy, relentlessness, rigidity, rigorism, steeliness, sternness, stiff temper, stiffness, toughness, unalterability, unbendingness, unchangeability, uncompromisingness, ungivingness, unrelentingness, unyieldingness