Obdurate is a formal word meaning stubborn. If you want to major in English, but your parents are obdurate that you should go premed, they might go so far as to threaten not to pay your tuition.

This adjective descends from Latin obdurare "to harden." A near synonym is adamant, from Latin adamas "hard metal, diamond." So both of these synonyms derive from the quality of hardness being associated with a stubborn personality.

Definitions of obdurate

adj stubbornly persistent in wrongdoing

cussed, obstinate, unrepentant
unregenerate, unregenerated
not reformed morally or spiritually

adj showing unfeeling resistance to tender feelings

“the child's misery would move even the most obdurate heart”
flint, flinty, granitic, stony
hardhearted, heartless
lacking in feeling or pity or warmth

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