The Collaborative International Dictionary of English v.0.48:

Miraculous \Mi*rac"u*lous\, a. [F. miraculeux. See Miracle.]
   [1913 Webster]
   1. Of the nature of a miracle; performed by supernatural
      power; effected by the direct agency of almighty power,
      and not by natural causes.
      [1913 Webster]

   2. Supernatural; wonderful.
      [1913 Webster]

   3. Wonder-working. "The miraculous harp." --Shak.
      [1913 Webster] -- Mi*rac"u*lous*ly, adv. --
      Mi*rac"u*lous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

miraculous
    adj 1: being or having the character of a miracle [syn:
           marvelous, marvellous, miraculous]
    2: peculiarly fortunate or appropriate; as if by divine
       intervention; "a heaven-sent rain saved the crops"; "a
       providential recovery" [syn: heaven-sent, providential,
       miraculous]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "miraculous":
   amazing, astonishing, astounding, beguiling, bewildering,
   bewitched, crazy, enchanted, enigmatic, exceptional, extraordinary,
   fabulous, fantastic, fascinating, incomprehensible, inconceivable,
   incredible, inexplicable, magical, marvelous, mind-boggling,
   necromantic, numinous, outlandish, passing strange, phenomenal,
   preternatural, prodigious, puzzling, rare, remarkable, sensational,
   spectacular, staggering, strange, striking, stupendous, superhuman,
   superior, supermundane, supernatural, supramundane, supranatural,
   thaumaturgic, unbelievable, unearthly, unexplainable, unheard-of,
   unimaginable, unique, unprecedented, wonder-working, wonderful,
   wondrous