acetonePronunciation: /ˈasɪtəʊn/Definition of acetone noun [mass noun] Chemistry a colourless volatile liquid ketone made by oxidizing isopropanol, used as an organic solvent and synthetic reagent. Alternative name: propanone; chemical formula: CH3COCH3 Origin: mid 19th century: from acetic acid + -oneacetone in other Oxford dictionaries Definition of acetone in the US English dictionary