The Collaborative International Dictionary of English v.0.48:

Mythologic \Myth`o*log"ic\, Mythological \Myth`o*log"ic*al\, a.
   [L. mythologicus: cf. F. mytholigique.]
   1. Of or pertaining to mythology or to myths; as,
      mythological creatures. -- Myth`o*log"ic*al*ly, adv.
      [1913 Webster]

   2. based on or told of in traditional stories; lacking
      factual basis or historical validity; mythical; fabulous.

   Syn: fabulous, mythic, mythical.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

mythological
    adj 1: based on or told of in traditional stories; lacking
           factual basis or historical validity; "mythical
           centaurs"; "the fabulous unicorn" [syn: fabulous,
           mythic, mythical, mythologic, mythological]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "mythological":
   acknowledged, admitted, allegoric, conventional, customary,
   established, fabulous, fictional, fictitious, fictive, figmental,
   fixed, folk, hallowed, handed down, heroic, hoary, immemorial,
   inveterate, legendary, long-established, long-standing,
   make-believe, mythic, mythicized, mythified, mythopoeic,
   mythopoetic, nonactual, nonfactual, nonrealistic, of long standing,
   of the folk, oral, parabolic, prescriptive, received, recognized,
   romantic, romanticized, rooted, time-honored, traditional,
   tried and true, true-blue, understood, unwritten, venerable,
   worshipful