Source : Webster's Revised Unabridged Dictionary (1913)

Carbonyl \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}.

Source : WordNet®

carbonyl
     adj : relating to or containing the carbonyl group [syn: {carbonylic}]

carbonyl
     n : a compound containing metal combined with carbon monoxide