/ferr'men tay"sheuhn/ , n.
1. the act or process of fermenting.
2. a change brought about by a ferment, as yeast enzymes, which convert grape sugar into ethyl alcohol.
3. agitation; excitement.
[ 1350-1400; ME fermentacioun fermentation- (s. of fermentatio ), equiv. to L fermentat ( us ) fermented (see FERMENT, -ATE 1 ) + -ion- -ION ]