noun
: a bitter deliquescent crystalline salt MgCl 2 that usually crystallizes with six molecules of water, that occurs in seawaters, natural brines, and salt deposits, that is obtained by recovery from seawater, brines, or carnallite or by chlorination of magnesia, and that is used chiefly in producing magnesium metal and magnesium oxychloride cements and as a fireproofing agent