Definitions of ferment:

• noun:   a substance capable of bringing about fermentation
• noun:   a chemical phenomenon in which an organic molecule splits into simpler substances
• noun:   a state of agitation or turbulent change or development

  Example: "The political ferment produced a new leadership"

• noun:   a process in which an agent causes an organic substance to break down into simpler substances; especially, the anaerobic breakdown of sugar into alcohol
• verb:   cause to undergo fermentation

  Example: "We ferment the grapes for a very long time to achieve high alcohol content"

• verb:   work up into agitation or excitement

  Example: "Islam is fermenting Africa"

• verb:   be in an agitated or excited state

  Example: "The Middle East is fermenting"

• verb:   go sour or spoil