carbonyl

Short definition from Wiktionary

Noun

1. 1
   A divalent functional group, (-CO-), characteristic of aldehydes, ketones, carboxylic acids, amides, carboxylic acid anhydrides, carbonyl halides, esters and others.
2. 2
   Any compound of a metal with carbon monoxide, such as nickel carbonyl, Ni(CO)₄.