inflexible

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

Antonyms: flexible reasonable willing yielding

Synonyms: hard immalleable impliable inelastic nonflexible rigid set starched taut unbending

Antonyms: bendable elastic flexible pliable pliant resilient soft