Definition of fantastic

• ludicrously odd; "Hamlets assumed antic disposition"; "fantastic Halloween costumes"; "a grotesque reflection in the mirror"
• extraordinarily good; 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"
• extravagantly fanciful and unrealistic; foolish; "a fantastic idea of his own importance"