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]