The Collaborative International Dictionary of English v.0.48:

Nonconformist \Non`con*form"ist\, n.
   One who does not conform to an established church;
   especially, one who does not conform to the established
   church of England; a dissenter.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nonconformist
    adj 1: not conforming to some norm or socially approved pattern
           of behavior or thought; "their rabidly nonconformist
           deportment has made them legendary"; "the old stubborn
           nonconformist spirit of the early settlers" [syn:
           nonconformist, unconformist] [ant: conformist]
    2: not conforming to established customs or doctrines especially
       in religion [syn: nonconforming, nonconformist]
    n 1: a Protestant in England who is not a member of the Church
         of England [syn: Nonconformist, chapelgoer] [ant:
         Anglican]
    2: someone who refuses to conform to established standards of
       conduct [syn: nonconformist, recusant] [ant:
       conformist]

Moby Thesaurus II by Grady Ward, 1.0:

191 Moby Thesaurus words for "nonconformist":
   Albigensian, Arian, Bohemian, Cathar, Donatist, Ebionite, Erastian,
   Gnostic, Jansenist, Lollard, Manichaean, Monophysite, Montanist,
   Pelagian, Sabellian, Waldensian, Wyclifite, agitator, alien,
   anomaly, antagonistic, antinomian, antipathetic, apostate, beatnik,
   brawler, breakaway, capricious, case, changeable, changing,
   character, choppy, clashing, conflicting, contradicting,
   contradictory, counteractant, counteracting, counteractive,
   countervailing, counterworking, crackpot, crank, cranky,
   crosspatch, crotchety, demurrer, deviant, deviating, deviative,
   deviatory, different, disorderly, dissenter, dissentient,
   dissident, divaricate, divergent, diversified, diversiform,
   dropout, eccentric, emanationist, erose, erratic, exception,
   extremist, fanatic, flake, flower child, freak, frondeur, heretic,
   heretical, hermit, heterodox, hippie, hobo, hostile, hylotheist,
   iconoclast, iconoclastic, impulsive, inconsistent, inconstant,
   individualist, individualistic, inimical, inner-directed,
   inner-directed person, insubordinate, insurgent, insurrectionary,
   insurrectionist, insurrecto, irregular, jagged, jerky, kook,
   lone wolf, loner, malcontent, maverick, mercurial, meshuggenah,
   misbeliever, misfit, motley, mutable, mutineer, natural, naysayer,
   nonconformer, nonconforming, nonjuror, nonstandard, nonuniform,
   nut, objector, odd fellow, oddball, oddity, opinionist, opposing,
   opposition voice, oppositional, oppugnant, original, outsider,
   pantheist, pariah, perverse, pluralistic, protestant, protester,
   queer duck, queer fish, queer specimen, radical, ragged, rara avis,
   reactionary, rebel, rebellious, recalcitrant, recluse, recusant,
   renegade, renitent, repugnant, resistant, revolter, revolutionary,
   revolutionist, rioter, rough, schismatic, screwball, sectarian,
   sectary, separatist, solitary, spasmodic, sporadic, sport,
   strange duck, subversive, swinger, traitor, tramp, type,
   ugly duckling, unconformist, unequable, unequal, uneven,
   unorthodox, unstable, unsteady, unsystematic, ununiform, variable,
   variegated, variform, various, varying, wavering, weirdo, yippie,
   zealot