Indefatigation is a rare word that means the quality of being tireless or untiring, and synonyms for this unique word include perseverance, tenacity, diligence, and never giving up. Indefatigation can also be related to unrelenting, resilient, unflagging, and unwavering. Other synonyms that capture the ultimate essence of this term are stamina, persistence, grit, determination, and steadfastness. When a person is going through a tough period in their life, it is essential to keep unwavering hope and maintain an indefatigation attitude. The idea is to never let anything bring you down; stay strong, sail through, and keep on moving forward.