Definition of onerous:
galling, tedious, grueling, causing care, heartbreaking, vexatious, ponderous, weighty, rigorous, tiresome, overpowering, fatiguing, rigorous, distressing, austere, embittering, tiring, overtaxing, plodding, pressing, responsible, exacting, afflictive, irksome, grievous, excessive, serious, heavy, exhausting, burdensome, merciless, taxing, weighty, effortful, exigent, painful, exacting, intolerable, backbreaking, backbreaking, crushing.
difficult (part of speech: adjective)
- "The Lesser Bourgeoisie", Honore de Balzac.
- "Edison, His Life and Inventions", Frank Lewis Dyer and Thomas Commerford Martin.
- "The Dop Doctor", Clotilde Inez Mary Graves.