The Collaborative International Dictionary of English v.0.48:

Revolutionist \Rev`o*lu"tion*ist\, n.
   One engaged in effecting a change of government; a favorer of
   revolution. --Burke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

revolutionist
    n 1: a radical supporter of political or social revolution [syn:
         revolutionist, revolutionary, subversive,
         subverter]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "revolutionist":
   Bolshevik, Bolshevist, Bolshie, Carbonarist, Carbonaro, Castroist,
   Castroite, Charley, Communist, Cong, Fenian, Guevarist, Jacobin,
   Jacobinic, Leninist, Maoist, Marxist, Mau-Mau, Puritan, Red,
   Red Republican, Roundhead, Sinn Feiner, Trotskyist, Trotskyite, VC,
   Vietcong, Wobbly, Yankee, Yankee Doodle, agin the government,
   agitator, anarch, anarchic, anarchist, anarchistic,
   anarcho-syndicalist, antinomian, bonnet rouge, brawler,
   criminal syndicalist, extreme, extreme left-winger, extremist,
   extremistic, fanatic, frondeur, insubordinate, insurgent,
   insurrectionary, insurrectionist, insurrecto, left-wing extremist,
   lunatic fringe, malcontent, maverick, mild radical, mildly radical,
   mutineer, nihilist, nihilistic, nonconformist, parlor Bolshevik,
   parlor pink, pink, pinko, rabid, radical, rebel, red, revolter,
   revolutional, revolutionary, revolutionary junta, revolutioner,
   revolutionizer, rioter, sans-culotte, sans-culottic,
   sans-culottish, sans-culottist, subversive, syndicalist, terrorist,
   traitor, ultra, ultraconservative, ultraist, ultraistic, yippie