The Collaborative International Dictionary of English v.0.48:

Ferment \Fer"ment\, n. [L. fermentum ferment (in senses 1 & 2),
   perh. for fervimentum, fr. fervere to be boiling hot, boil,
   ferment: cf. F. ferment. Cf. 1st Barm, Fervent.]
   1. That which causes fermentation, as yeast, barm, or
      fermenting beer.
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   Note: Ferments are of two kinds: (a) Formed or organized
         ferments. (b) Unorganized or structureless ferments.
         The latter are now called enzymes and were formerly
         called soluble ferments or chemical ferments.
         Ferments of the first class are as a rule simple
         microscopic vegetable organisms, and the fermentations
         which they engender are due to their growth and
         development; as, the acetic ferment, the butyric
         ferment, etc. See Fermentation. Ferments of the
         second class, on the other hand, are chemical
         substances; as a rule they are proteins soluble in
         glycerin and precipitated by alcohol. In action they
         are catalytic and, mainly, hydrolytic. Good examples
         are pepsin of the dastric juice, ptyalin of the salvia,
         and disease of malt. Before 1960 the term "ferment" to
         mean "enzyme" fell out of use. Enzymes are now known to
         be globular proteins, capable of catalyzing a wide
         variety of chemical reactions, not merely hydrolytic.
         The full set of enzymes causing production of ethyl
         alcohol from sugar has been identified and individually
         purified and studied. See enzyme.
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   2. Intestine motion; heat; tumult; agitation.
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            Subdue and cool the ferment of desire. --Rogers.
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            the nation is in a ferment.           --Walpole.
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   3. A gentle internal motion of the constituent parts of a
      fluid; fermentation. [R.]
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            Down to the lowest lees the ferment ran. --Thomson.
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   ferment oils, volatile oils produced by the fermentation of
      plants, and not originally contained in them. These were
      the quintessences of the alchemists. --Ure.
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