\Car"bon*yl\, n. [Carbon + -yl.] (Chem.)
The radical {(CO)''}, occuring, always combined, in many
compounds, as the aldehydes, the ketones, urea, carbonyl
chloride, etc.
Note: Though denoted by a formula identical with that of
      carbon monoxide, it is chemically distinct, as carbon
      seems to be divalent in carbon monoxide, but
      tetravalent in carbonyl compounds.
{Carbonyl chloride} (Chem.), a colorless gas, {COCl2}, of
   offensive odor, and easily condensable to liquid. It is
   formed from chlorine and carbon monoxide, under the
   influence of light, and hence has been called {phosgene
   gas}; -- called also {carbon oxychloride}.