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]