Source : Webster's Revised Unabridged Dictionary (1913)

Fermentation \Fer`men*ta"tion\, n. [Cf. F. fermentation.]
   1. The process of undergoing an effervescent change, as by
      the action of yeast; in a wider sense (Physiol. Chem.),
      the transformation of an organic substance into new
      compounds by the action of a ferment, either formed or
      unorganized. It differs in kind according to the nature of
      the ferment which causes it.

Source : WordNet®

fermentation
     n 1: a process in which an agent causes an organic substance to
          break down into simpler substances; especially, the
          anaerobic breakdown of sugar into alcohol [syn: {zymosis},
           {zymolysis}, {fermenting}, {ferment}]
     2: a state of agitation or turbulent change or development;
        "the political ferment produced a new leadership"; "social
        unrest" [syn: {agitation}, {ferment}, {unrest}]
     3: a chemical phenomenon in which an organic molecule splits
        into simpler substances [syn: {ferment}]