"heavy water." YourDictionary, n.d. Web. 19 September 2018. <http://www.yourdictionary.com/heavy-water>.
heavy water. (n.d.). Retrieved September 19th, 2018, from http://www.yourdictionary.com/heavy-water
Either of two isotopic forms of water, especially deuterium oxide, consisting chiefly of molecules that contain deuterium instead of protium. Heavy water is used as a moderator in certain nuclear reactors.