What does "tirelessness" mean?

The property of being tireless.

Tirelessness

Common synonyms include: indefatigability, application, ardor, assiduity, concentration, constancy.

noun

noun ·Rare ·Advanced level

Noun

1
The property of being tireless. uncountable
"His tirelessness in helping the poor won him an award and a nervous breakdown from exhaustion."
2
tireless determination wordnet

"His tirelessness in helping the poor won him an award and a nervous breakdown from exhaustion."

From tireless + -ness.