Low rounded bowl for waste water to be used for rinsing tea bowls (chawan) during the Japanese tea ceremony. Either hot or cold water is poured into this after a Chawan has been rinsed during a tea ceremony. It could be made of metal, clay or plain, thin wood bent into a shallow cylindrical shape.
Bowl-shaped Kensui are most common. Some kensui are lacquered. A clean Kensui is used for each tea ceremony. Disposing of the waste water is considered an unclean task and reuse in front of guests is considered a discourtesy.