ferment

verb

1. To react, using fermentation; especially to produce alcohol by aging or by allowing yeast to act on sugars; to brew.
2. To stir up, agitate, cause unrest or excitement in.

   “Ye vigorous swains! while youth ferments your blood.”

   “Pleas'd have I wander'd thro' your rough domain; / Trod the pure virgin-ſnows, myſelf as pure; / Heard the winds roar, and the big torrent burſt; / Or ſeen the deep fermenting tempeſt brew'd, / In the grim evening ſky.”

noun

1. Something, such as a yeast or barm, that causes fermentation.
2. A state of agitation or of turbulent change.

   “Subdue and cool the ferment of desire.”

   “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.”

   “Proponents of the broken windows theory assume that [disorder] means a neighborhood has lost control and doesn't care about crime. But surely there are other plausible meanings. It could signal artistic ferment, a youth hangout, rebellion, or an alternative lifestyle.”

3. A gentle internal motion of the constituent parts of a fluid; fermentation.

   “A Rage of Pleaſure madden'd every Breaſt, / Down to the loweſt Lees the Ferment ran: [...]”

4. A catalyst.