indefatigable (adj.) Incapable of defeat, failure, decay Despite having worked a long shift, the indefatigable employee stayed late to cover for a sick coworker. Despite working long hours, she remained indefatigable, never showing signs of exhaustion. His indefatigable spirit kept him pushing forward, even when the odds were against him. The indefatigable researcher spent years searching for a cure, refusing to give up. With indefatigable determination, the athlete trained every day to achieve his goal.( A good example is Neeraj Chopra) The volunteers were indefatigable, tirelessly helping those in need after the disaster. Another good example is The Mountain Man.