The Collaborative International Dictionary of English v.0.48:

Schismatical \Schis*mat"ic*al\, a.
   Same as Schismatic. -- Schis*mat"ic*al*ly, adv. --
   Schis*mat"ic*al*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

schismatical
    adj 1: of or relating to or involved in or characteristic of
           schism; "schismatic sects" [syn: schismatic,
           schismatical]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "schismatical":
   abjuratory, alienated, antiestablishment, at odds with,
   at variance with, breakaway, counter-culture, denominational,
   differing, disagreeing, dissentient, dissenting, dissident,
   in opposition, mugwumpian, mugwumpish, nonconforming, opposing,
   recusant, renunciative, renunciatory, repudiative, repudiatory,
   revocatory, schismatic, secessionist, sectarian, sectary,
   separatist, underground