Onerous means burdensome, oppressive, or requiring a great deal of effort to complete. When a task is onerous, it weighs you down with difficulty or demands more than seems reasonable.

A teacher might assign an onerous amount of homework: fifty math problems, three chapters of reading, and a full essay, all due the next day. The work feels crushing under its weight. An onerous responsibility might be caring for five younger siblings every afternoon while also trying to finish your own schoolwork.

Onerous things feel like heavy loads you must carry. An onerous rule might require students to handwrite every assignment in perfect cursive with no mistakes allowed. An onerous process might involve filling out twenty forms just to check out a library book.

When something is onerous, it's unreasonably difficult or demanding, beyond normal hardship. Practicing piano for thirty minutes feels like regular work. Practicing for three hours with no breaks while copying each piece ten times? That's onerous. The weight of onerous tasks can exhaust people, making simple obligations feel like carrying boulders uphill.