Mikveh Definition A mikveh is a ritual bath. According traditional Jewish law, to be ritually fit for use, persons and objects must be immersed in a mikveh. A mikveh has to contain enough water to cover the body of a woman of average size and the water has to come from a natural spring or a river. [NSJE:658] [14K] Mikveh under construction, January, 1995. Congregation Beis Menachem (formerly Tiphereth Israel) Chabad of Greater Phoenix. Photo by Sheila Smolensky