extremist

• POS: Adjective, Noun
• HYPHEN: ex=trem=ist

CIDE DICTIONARY

extremist, n. 

 A supporter of extreme doctrines or practice; one who holds extreme opinions.  [1913 Webster]

OXFORD DICTIONARY

extremist, n. (also attrib.) a person who holds extreme or fanatical political or religious views and esp. resorts to or advocates extreme action.

Derivative

extremism n.

THESAURUS

extremist

Bolshevik, Fabian, Jacobin, Wobbly, agitator, anarchist, anarchistic, anarcho-syndicalist, bigoted, brawler, extravagant, extreme, extreme left-winger, extremistic, fanatic, frondeur, haggard, inordinate, insubordinate, insurgent, insurrectionary, insurrectionist, insurrecto, irrational, left-wing extremist, lunatic fringe, malcontent, maverick, meliorist, mild radical, mildly radical, mutineer, nihilist, nihilistic, nonconformist, overenthusiastic, overreligious, overzealous, parlor Bolshevik, parlor pink, perfervid, pink, pinko, progressionist, progressist, progressive, progressivist, rabid, radical, rebel, red, reformer, reformist, revisionist, revolter, revolutional, revolutionary, revolutionist, rioter, sans-culotte, subversive, syndicalist, traitor, ultra, ultraconservative, ultraist, ultraistic, ultrazealous, unreasonable, utopian, utopist, wild-eyed, wild-looking, yippie, zealotic