Source : Webster's Revised Unabridged Dictionary (1913)

   3. A gentle internal motion of the constituent parts of a
      fluid; fermentation. [R.]

            Down to the lowest lees the ferment ran. --Thomson.

   {ferment oils}, volatile oils produced by the fermentation of
      plants, and not originally contained in them. These were
      the quintessences of the alchenists. --Ure.