secessionist

noun

1. A person who secedes or supports secession from a political union or an alliance or organisation.

   “Near-synonym: separatist”

   “Gustav Klimt was of the Viennese secessionist school.”

adj

1. Seceding or supporting secession.

   “The principality of Freedonia (www.freedonia.org), an earnest collective of secessionist superlibertarians based in Boston, falls into the first category.”