Tireless determination.

synonyms: indefatigableness, tirelessness.

Roget 604a: perseverance; continuance etc. (inaction) 143; permanence etc. (absence of change) 141; firmness etc. (stability) 150.    constancy, steadiness; singleness of purpose, tenacity of purpose; persistence, plodding, patience; sedulity etc. (industry) 682; pertinacy^†, pertinacity, pertinaciousness; iteration etc. 104; bottom, game, pluck, stamina, backbone, grit; indefatigability, indefatigableness; bulldog courage.    ... show more