hard water: water that contains mineral salts (as calcium and magnesium ions) that limit the formation of lather with soap
water: binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 degrees centigrade and boils above 100 degrees centigrade; widely used as a solvent
firelighter: (a piece of) a substance that burns easily and can be used to start a coal or coke fire