I was indefatigable when it came to the championship basketball game.
When all of the other track layers had collapsed from exhaustion, the indefatigable Casey Jones continued laying track for eighteen hours without showing the least sign of fatigue.
Forrest Gump ran for so long, he was thought to be indefatigable.
Dr. Martin Luther King, Jr. was known as an inegatigable worker for civil rights.
John Henry, the folk legend of a railroad worker, was considered indefatigable, as he could dig through a mountain himself.