Webster’s Revised Unabridged Dictionary · 1913 Hydrarthrosis Hy′drar·thro′sis (hī′drär·thrō′sĭs), n. [NL. See Hydro-, 1, and Arthrosis.] (Med.) An effusion of watery liquid into the cavity of a joint. ‹ Hydrargyrum Hydrastine ›