pi·nac·o·lone \-ˌlōn\noun (-s) Etymology:pinacol + -one 1.: a liquid ketone (CH3)3COCH3 of peppermint odor formed from pinacol by treatment with acid to cause loss of water and molecular rearrangement; 3,3-dimethyl-2-butanone 2.: any of a series of ketones R3CCOR formed like pinacolone from other pinacols