- a poisonous, colorless, very volatile liquid or suffocating gas, COCl2, a chemical-warfare compound: used chiefly in organic synthesis.
- a colourless easily liquefied poisonous gas, carbonyl chloride, with an odour resembling that of new-mown hay: used in chemical warfare as a lethal choking agent and in the manufacture of pesticides, dyes, and polyurethane resins. Formula: COCl 2
