The Collaborative International Dictionary of English v.0.48:

Theistic \The*is"tic\, Theistical \The*is"tic*al\, a.
   Of or pertaining to theism, or a theist; according to the
   doctrine of theists.
   [1913 Webster]

WordNet (r) 3.0 (2006):

theistic
    adj 1: of or relating to theism [syn: theist, theistical,
           theistic]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "theistic":
   Christian, Christianlike, Christianly, Cyrenaic, Eleatic,
   Epicurean, Megarian, Stoic, adoring, animist, animistic,
   anthropomorphic, anthropotheistic, atomistic, believing,
   cosmotheistic, cultish, cultist, cultistic, deistic, devoted,
   devout, ditheistic, dutiful, eclectic, empirical, eudaemonistic,
   existential, faithful, hedonic, hedonist, hedonistic, humanist,
   humanistic, idealistic, instrumentalist, materialistic,
   mechanistic, metaphysical, monistic, monotheistic, naturalistic,
   nominalist, panlogistical, pantheistic, physicomorphic, pietistic,
   pious, polytheistic, positivist, positivistic, pragmatic,
   pragmatist, prayerful, rationalistic, realist, realistic,
   religious, reverent, reverential, scholastic, sensationalistic,
   solemn, syncretistic, transcendentalist, transcendentalistic,
   tritheistic, utilitarian, venerational, venerative, vitalistic,
   voluntarist, voluntaristic, worshipful