os·te·o·ar·thri·tis (ŏs'tē-ō-är-thrī'tĭs) n. A form of arthritis, occurring mainly in older persons, that is characterized by chronic degeneration of the cartilage of the joints. Also called degenerative joint disease. os'te·o·ar·thrit'ic (-thrĭt'ĭk) adj.