/ ˈædəmənt; NAmE / adjective
determined not to change your mind or to be persuaded about sth :
Eva was adamant that she would not come.
► ad·am·ant·ly adverb :
His family were adamantly opposed to the marriage.
••
WORD ORIGIN
Old English (as a noun), from Old French adamaunt- , via Latin from Greek adamas , adamant- , untameable, invincible (later used to denote the hardest metal or stone, hence diamond), from a- not + daman to tame.