What does onerous mean?

Onerous is an adjective used to describe something of huge difficulty or something that causes great trouble. If you attempted to do a challenge of wearing over a hundred outfits in under 24 hours, your laundry work would be onerous.

Sentence example: Jensen sighed as he thought about his onerous task of organizing the disorderly bookshelf.

Synonym examples of onerous: difficult, tough, arduous, laborious, enervating