To react, using fermentation; especially to produce alcohol by aging or by allowing yeast to act on sugars; to brew.
To stir up, agitate, cause unrest or excitement in.
noun
Something, such as a yeast or barm, that causes fermentation.
A state of agitation or of turbulent change.
14 November, 1770, Junius, letter to the Right Honourable Lord Mansfield
The nation is in a ferment.
Clad in a Persian-Renaissance gown and a widow's tiara of white batiste, Mrs Thoroughfare, in all the ferment of a Marriage-Christening, left her chamber on vapoury autumn day and descending a few stairs, and climbing a few others, knocked a trifle brusquely at her son's wife's door.
A gentle internal motion of the constituent parts of a fluid; fermentation.