Source : Webster's Revised Unabridged Dictionary (1913)

Mesityl \Mes"i*tyl\, n. (Chem.)
   A hypothetical radical formerly supposed to exist in mesityl
   oxide.

   {Mesityl oxide} (Chem.), a volatile liquid having the odor of
      peppermint, obtained by certain dehydrating agents from
      acetone; -- formerly called also {dumasin}.