Fermentation

noun

1. Any of a group of chemical reactions induced by microorganisms or enzymes that split complex organic compounds into relatively simple substances, especially the anaerobic conversion of sugar to carbon dioxide and alcohol by yeast.
2. Unrest; agitation.
3. A gentle boiling or ebullition.
4. A decomposition produced in an organic substance by the physiological action of a living organism or by certain unorganized agents. See ferment.
5. Figuratively, the state of being in high activity or commotion; agitation; excitement, as of the intellect or feelings, a society, etc.