The Collaborative International Dictionary of English v.0.48:

Zymosis \Zy*mo"sis\, n. [NL., fr. Gr. ? fermentation, fr. ?
   ferment.] (Med.)
   (a) A fermentation; hence, an analogous process by which an
       infectious disease is believed to be developed.
   (b) A zymotic disease. [R.]
       [1913 Webster]

WordNet (r) 3.0 (2006):

zymosis
    n 1: a process in which an agent causes an organic substance to
         break down into simpler substances; especially, the
         anaerobic breakdown of sugar into alcohol [syn: zymosis,
         zymolysis, fermentation, fermenting, ferment]
    2: (medicine) the development and spread of an infectious
       disease (especially one caused by a fungus)