imposing or constituting a physical, mental, or figurative load which can be borne only with effort; burdensome.

In an onerous manner.

The state or characteristic of being onerous.

plural of onerousness

(obsolete) To load; to burden.

Alternative form of in a one-er

(informal) An extraordinary individual. / A small marble of little worth in children's games. / (UK) A conker that has won one match.

(obsolete) The act of loading.

plural of oner

simple past tense and past participle of onerate