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]