The Collaborative International Dictionary of English v.0.48:

Misfit \Mis*fit"\, n.
   1. The act or the state of fitting badly; as, a misfit in
      making a coat; a ludicrous misfit.
      [1913 Webster]

   2. Something that fits badly, as a garment.
      [1913 Webster]

            I saw an uneasy change in Mr. Micawber, which sat
            tightly on him, as if his new duties were a misfit.
                                                  --Dickens.
      [1913 Webster]

   3. A person who does not fit in comfortably with the
      surrounding situation or society; one who cannot conform
      or adjust to the circumstances in which he lives.
      [PJC]

WordNet (r) 3.0 (2006):

misfit
    n 1: someone unable to adapt to their circumstances

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "misfit":
   Bohemian, anomaly, beatnik, black sheep, blemish, crosspatch,
   deviant, dissenter, dropout, eccentric, flower child, foreign body,
   foreign intruder, freak, heretic, hippie, impurity, individual,
   individualist, inner-directed person, intruder, maverick,
   monkey wrench, mote, naysayer, nonconformist, nonjuror, oddball,
   original, sectarian, sectary, sliver, speck, splinter, sport,
   stone, swinger, ugly duckling, unconformist, weed, yippie