The Oxford Thesaurus An A-Z Dictionary of Synonyms - fantastic adj.

1) fanciful, strange, weird, peculiar, odd, eccentric, queer, bizarre, quaint, outlandish, exotic, extravagant, grotesque, nightmarish, alien, remarkable: She wore the most fantastic costume to the fancy-dress ball. 2) imaginary, illusory, illusive, unreal, visionary, fanciful, unrealistic, imagined, irrational: His books are inhabited by fantastic creatures. 3) unbelievable, incredible, preposterous, extraordinary, implausible, absurd, unlikely: At 85, he made the fantastic decision to enter the marathon. 4) marvellous, spectacular, splendid, wonderful, tremendous, overwhelming, Colloq great, fabulous, terrific: The Picasso exhibition is simply fantastic.