The Collaborative International Dictionary of English v.0.48:

Cowpox \Cow"pox`\ (-p[o^]ks`), n. (Med.)
   A pustular eruptive disease of the cow, which, when
   communicated to the human system, as by vaccination, protects
   from the smallpox; vaccinia; -- called also kinepox,
   cowpock, and kinepock. --Dunglison.
   [1913 Webster]