noun
fruitless effort; wasted effort; futility
Refers to effort that yields no result; often used in formal or written contexts. The gloss 'abortive scheme' is a narrower, less common nuance.
彼の努力は結局徒労に終わった。
His efforts ended up being in vain.
そんなことをしても徒労に過ぎない。
Doing that would be nothing but wasted effort.
Compound of 徒 (futile, vain) and 労 (labor, effort). The exact historical derivation is uncertain, but the meaning is transparent from the kanji components.