1. Uncooperative and irritable.
2. Meager (stingy), whether out of poverty or lack of generosity.
3. Etymology: from about 1816, American Enlgish dialectal contraction of "ordinary". "Commonplace", hence "of poor quality, coarse, ugly." By about 1860, the sense had evolved to being "mean, cantankerous."

These words are NOT related to this onus-, oner- family. They were placed here simply to point out that they are not relatives of those words that are derived from the Latin sources of this unit.