fantastic in WordNet English dictionary

1. ludicrously odd
   "Hamlet's assumed antic disposition"; "fantastic Halloween costumes"; "a grotesque reflection in the mirror"
   antic  fantastic  fantastical  grotesque 
   
2. 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"
   fantastic  grand  howling  marvelous  marvellous  rattling  terrific  tremendous  wonderful  wondrous 
   
3. extravagantly fanciful in design, construction, appearance
   "Gaudi's fantastic architecture"
   fantastic 
   
4. existing in fancy only
   "fantastic figures with bulbous heads the circumference of a bushel"- Nathaniel Hawthorne
   fantastic  fantastical 
   
5. fanciful and unrealistic; foolish
   "a fantastic idea of his own importance"
   fantastic  wild