The Collaborative International Dictionary of English v.0.48:

Mythic \Myth"ic\, Mythical \Myth"ic*al\, a. [L. mythicus, Gr. ?.
   See Myth.]
   Of or relating to myths; described in a myth; of the nature
   of a myth; fabulous; imaginary; fanciful; mythological. --
   Myth"ic*al*ly, adv.
   [1913 Webster]

         The mythic turf where danced the nymphs. --Mrs.
                                                  Browning.
   [1913 Webster]

         Hengist and Horsa, Vortigern and Rowena, Arthur and
         Mordred, are mythical persons, whose very existence may
         be questioned.                           --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mythical
    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:

83 Moby Thesaurus words for "mythical":
   acclaimed, allegoric, allegorical, celebrated, chimerical,
   concocted, cooked-up, created, distinguished, exceptional,
   extraordinary, fabled, fabricated, fabulous, famed, famous,
   fancied, fanciful, fantasied, fantastic, far-famed, far-heard,
   fictional, fictitious, fictive, figmental, forged, hatched,
   honored, imaginary, indescribable, ineffable, invented, legendary,
   made-up, make-believe, manufactured, marked, marvelous,
   much acclaimed, mythic, mythicized, mythified, mythological,
   mythopoeic, mythopoetic, nonactual, nonfactual, nonrealistic,
   notable, noted, noteworthy, notorious, of mark, of note, parabolic,
   phenomenal, popular, portentous, prodigious, put-up, remarkable,
   renowned, romantic, romanticized, storied, stupefying, stupendous,
   supposititious, symbolic, talked-about, talked-of, traditional,
   trumped-up, unexampled, unparalleled, unprecedented, unreal,
   unspeakable, untrue, visionary, well-known, wonderful