The Collaborative International Dictionary of English v.0.48:

Wonderful \Won"der*ful\, a.
   Adapted to excite wonder or admiration; surprising; strange;
   astonishing.
   [1913 Webster]

   Syn: Marvelous; amazing. See Marvelous.
        [1913 Webster] -- Won"der*ful*ly, adv. --
        Won"der*ful*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

wonderful
    adj 1: extraordinarily good or great ; used especially as
           intensifiers; "a fantastic trip to the Orient"; "the film
           was fantastic!"; "a howling success"; "a marvelous
           collection of rare books"; "had a rattling conversation
           about politics"; "a tremendous achievement" [syn:
           fantastic, grand, howling(a), marvelous,
           marvellous, rattling(a), terrific, tremendous,
           wonderful, wondrous]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "wonderful":
   amazing, appalling, astonishing, astounding, beguiling,
   bewildering, conspicuous, cool, divine, egregious, enigmatic,
   exceptional, exquisite, extraordinary, fabulous, fantastic,
   fascinating, formidable, gilt-edged, glorious, golden, groovy,
   heavenly, immense, incomprehensible, inconceivable, incredible,
   indescribable, ineffable, legendary, magnificent, marked,
   marvelous, miraculous, mythical, notable, noteworthy, noticeable,
   of mark, outlandish, outstanding, passing strange, peachy,
   phenomenal, portentous, prodigious, puzzling, rare, remarkable,
   sensational, signal, splendid, splendiferous, staggering, sterling,
   strange, striking, stupefying, stupendous, super, superb,
   supereminent, superexcellent, superfine, superior, surprising,
   swell, terrific, tremendous, uncommon, unexampled, unheard-of,
   unimaginable, unique, unparalleled, unprecedented, unspeakable,
   wondrous