Definition of coalitionism in English:
coalitionism
noun ˌkəʊəˈlɪʃ(ə)nɪz(ə)mˌkəʊəˈlɪʃənɪz(ə)m
Government by coalition; the principles or advocacy of this.
Origin
Mid 19th century; earliest use found in Vermont Watchman & State Journal. From coalition + -ism.