1 cultist, cultish, clannish, cliquish, partisan, partial, dogmatic, doctrinaire, factional:
They seldom mingle with others, maintaining their sectarian existence.
2 parochial, narrow, narrow-minded, limited, insular, provincial, rigid, fanatic(al), prejudicial, prejudiced, bigoted:
Because they refused to consider ideas other than their own, they gradually became more and more sectarian in their views.
3 adherent, member, sectary, votary, cultist, partisan:
They tried to banish Anabaptists, Lutherans, Calvinists, and other sectarians
4 (true) believer, dogmatist, fanatic, bigot, zealot, extremist, Slang nut, bug, fiend:
Some of the sectarians engage in the ritualistic handling of live rattlesnakes.