seceder

noun

1. One who secedes, such as from a country or organization

   “But an express law included all these seceders in the general proscription; alledging, with a candour not usual, that those who assumed rank were, in fact, more criminal than such as were guilty of being born to it.”

   “If we now recognize this doctrine by allowing the seceders to go in peace, it is difficult to see what we can do if others choose to go or to extort terms upon which they will promise to remain.”

   “When Clive saw Rosalie Faithorn saunter in with James Allys he stared, but that young seceder from his own set greeted him without embarrassment and lighted a cigarette.”

2. (historical)A follower of the 18th-century secession movement from the Church of Scotland.
3. (rare)A member of the Free Presbyterian Church of Scotland.