The Collaborative International Dictionary of English v.0.48:

Partisan \Par"ti*san\, a. [Written also partizan.]
   1. Adherent to a party or faction; especially, having the
      character of blind, passionate, or unreasonable adherence
      to a party; as, blinded by partisan zeal.
      [1913 Webster]

   2. (Mil.) Serving as a partisan in a detached command; as, a
      partisan officer or corps.
      [1913 Webster]

   Partisan ranger (Mil.), a member of a partisan corps.
      [1913 Webster]