Source : Webster's Revised Unabridged Dictionary (1913)

Ketone \Ke"tone\ (k[=e]"t[=o]n), n. [Cf. {Acetone}.] (Chem.)
   One of a large class of organic substances resembling the
   aldehydes, obtained by the distillation of certain salts of
   organic acids and consisting of carbonyl ({CO}) united with
   two hydrocarbon radicals. In general the ketones are
   colorless volatile liquids having a pungent ethereal odor.

   Note: The ketones are named by adding the suffix-one to the
         stems of the organic acids from which they are
         respectively derived; thus, acetic acid gives acetone;
         butyric acid, butyrone, etc.

Source : WordNet®

ketone
     n : any of a class of organic compounds having a carbonyl group
         linked to a carbon atom in each of two hydrocarbon
         radicals