carbonyl

n. chemical compound containing metal and carbon monoxide

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl); in this situation, carbon is triple-bonded to oxygen : C≡O. The remainder of this article concerns itself with the organic chemistry definition of carbonyl.
See more at Wikipedia.org...

n. carbonyl, chemical compound containing metal and carbon monoxide

(n.)
The radical (CO)'', occuring, always combined, in many compounds, as the aldehydes, the ketones, urea, carbonyl chloride, etc.
  

 Say it 
A divalent group consisting of a carbon atom with a double-bond to oxygen. For example, acetone (CH3-(C=O)-CH3) is a carbonyl group linking two methyl groups. Also refers to a compound of a metal with carbon monoxide , such as iron carbonyl, Fe(CO)5.