adamant
definition
unyielding in attitude or opinion in spite of all appeals or urging
example
Despite numerous requests for reconsideration, she remained adamant in her decision to refuse the offer.
synonyms
inflexibleunyieldingresolute
word origin — from Middle French 'adamant', from Latin 'adamans', from Greek 'ἀδάμας' (adamas) meaning 'untameable, invincible'