"To die hard" is an idiomatic expression that refers to someone who is determined and persevering in their beliefs or actions, even in the face of adversity. Synonyms for this phrase include resolute, tenacious, persistent, unwavering, unyielding, and staunch. These words share the underlying meaning of showing steadfastness and determination. The term "resolute" suggests a firm resolve, while "tenacious" denotes hanging on to something strongly. "Persistent" implies an unwavering determination, and "unyielding" suggests an inflexible attitude. "Staunch" portrays a steadfast loyalty and unwavering dedication. All these synonyms embody the spirit of someone who possesses an indomitable will and refuses to give up easily, even when faced with difficult challenges.