secessionist adjective 1noun 1forms 3 adjective1 •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. — 2000 noun1 •A person who secedes or supports secession from a political union or an alliance or organisation.Gustav Klimt was of the Viennese secessionist school. formssecessionists · more secessionist · most secessionist