adamant immutable intractable obstinate resolute rigid rigorous steadfast strict stringent uncompromising unyielding adamantine determined dogged dyed-in-the-wool firm fixed hard hard-and-fast immovable implacable indomitable inexorable iron obdurate relentless set set in one's ways single-minded stand one's ground staunch steely stiff unadaptable unbending unchangeable uncompliant unrelenting unswayable