noun
: a chloride of mercury: as
a. : calomel
b. : a heavy transparent crystalline poisonous compound HgCl 2 made usually by heating mercury with gaseous chlorine or by subliming a mixture of mercury sulfate and common salt and used chiefly as a disinfectant and fungicide, in making other mercury compounds, and in photography — called also corrosive sublimate, mercuric chloride, mercury(II) chloride