The Collaborative International Dictionary of English v.0.48:

Sectarian \Sec*ta"ri*an\, a.
   Pertaining to a sect, or to sects; peculiar to a sect;
   bigotedly attached to the tenets and interests of a
   denomination; as, sectarian principles or prejudices.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sectarian \Sec*ta"ri*an\, n.
   One of a sect; a member or adherent of a special school,
   denomination, or religious or philosophical party; one of a
   party in religion which has separated itself from established
   church, or which holds tenets different from those of the
   prevailing denomination in a state.
   [1913 Webster]

   Syn: See Heretic.
        [1913 Webster]

WordNet (r) 3.0 (2006):

sectarian
    adj 1: of or relating to or characteristic of a sect or sects;
           "sectarian differences"
    2: belonging to or characteristic of a sect; "a sectarian mind";
       "the negations of sectarian ideology"- Sidney Hook;
       "sectarian squabbles in psychology" [ant: nonsectarian,
       unsectarian]
    n 1: a member of a sect; "most sectarians are intolerant of the
         views of any other sect" [syn: sectarian, sectary,
         sectarist]

Moby Thesaurus II by Grady Ward, 1.0:

108 Moby Thesaurus words for "sectarian":
   Bohemian, adherent, alienated, antiestablishment, apostate,
   at odds with, at variance with, beatification, beatitude, beatnik,
   bigot, bigoted, blessedness, blessing, breakaway, bug,
   canonization, clannish, cliquish, consecration, counter-culture,
   cultish, cultist, dedication, demurrer, denominational,
   denominationalist, deviant, devotion, differing, disagreeing,
   dissenter, dissentient, dissenting, dissident, doctrinaire,
   dogmatic, dogmatist, dropout, enshrinement, exaltation, extremist,
   factional, factionist, fanatic, fanatical, fiend, flower child,
   freak, glorification, grace, hallowing, heretic, heterodox, hippie,
   in opposition, insular, interested, justification,
   justification by works, limited, local, maverick, member, misfit,
   narrow, narrow-minded, nonconforming, nonconformist, nonjuror, nut,
   objector, opinionist, opposing, opposition voice, original,
   parochial, partial, partisan, party, prejudiced, prejudicial,
   protestant, protester, provincial, purification, recusant, rigid,
   sainthood, sainting, sanctification, schismatic, sectary,
   sectional, separatist, setting apart, small-town, splinter,
   state of grace, swinger, true believer, ugly duckling,
   unconformist, underground, unorthodox, votary, yippie, zealot