seceder

from The Collaborative International Dictionary of English v.0.48

Seceder \Se*ced"er\, n.
   1. One who secedes.
      [1913 Webster]

   2. (Eccl. Hist.) One of a numerous body of Presbyterians in
      Scotland who seceded from the communion of the Established
      Church, about the year 1733, and formed the Secession
      Church, so called.
      [1913 Webster]