A molecular group in which an oxygen atom is double-bonded to a carbon atom: O=C. The carbon atom then has two additional bonds to attach to the rest of the molecule. Organic molecules containing a carbonyl group are a very important, major group of compounds studied in the field of organic chemistry.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.