na-adjective
stubborn; obstinate; inflexible
Describes a person, attitude, or refusal that is unyielding and resistant to change or persuasion. Often carries a negative nuance of unreasonable rigidity.
彼は頑なに自分の意見を変えようとしなかった。
He stubbornly refused to change his opinion.
その老人は頑なで、誰の助言も聞かなかった。
The old man was obstinate and wouldn't listen to anyone's advice.