Lasting for a very long time; protracted; prolonged; time-consuming.
这项学术研究非常深入，预计会旷日长久才能得出最终成果。
This academic research is very in-depth, and it is expected to be long-drawn-out before final results can be obtained.
Next Idiom
Lasting for a very long time; protracted; prolonged; time-consuming.