Hy"dra*gogue (?), a. [L. hydragogus conveying off water, Gr. &?;; "y`dwr water + &?; to lead: cf. F. hydragogue.] (Med.) Causing a discharge of water; expelling serum effused into any part of the body, as in dropsy. -- n. A hydragogue medicine, usually a cathartic or diuretic.