Despite repeated attempts to persuade him, he remained obdurate and refused to change his mind.

obdurate 是形容词，由前缀 ob-（表示"反对、对抗"）和词根 dur（来自拉丁语 durus，意为"坚硬"）加上形容词后缀 -ate 构成。字面意思是"像石头一样坚硬的"，引申为"固执的、顽固不化的"。