fer·ment 
(fûrmĕnt′)
(fûrmĕnt′)n.
1.
a. An agent, such as an enzyme, bacterium, or fungus, that brings about fermentation.
b. Fermentation.
2.
a. A state of agitation or of turbulent change or development.
b. An agent that precipitates or is capable of precipitating such a state; a catalyst.
v. (fər-mĕnt) fer·ment·ed, fer·ment·ing, fer·ments
v.intr.
1. To undergo fermentation: cabbage that has fermented.
2. To develop in a turbulent or agitated way; seethe: an idea that was fermenting in his mind for months.
v.tr.
1. To cause to undergo fermentation: Yeasts ferment sugars.
2. To produce by or as if by fermentation: ferment the wine in oak barrels; hostility that was fermented by envy.
3. To make turbulent; excite or agitate: a fiery speech that fermented the crowd.
[Middle English, from Old French, from Latin fermentum; see bhreu- in the Appendix of Indo-European roots.]
fer·ment′a·bili·ty n.
fer·menta·ble adj.