They were singing discordantly, arduously, and with great effort, evidently not because they wished to sing, but because they wanted to show they were drunk and on a spree.
The idea of being made a fool of and of having thrown away that whole month of arduous melancholy service to Julie, and of seeing all the revenue from the Penza estates which he had already mentally apportioned and put to proper use fall into the hands of another, and especially into the hands of that idiot Anatole, pained Boris.
There are no more uses of "arduous" in the book.
Show samples from other sources
At last, they won their long and arduous fight for independence.
She undertook the arduous work of caring for twins.