conceived or appearing as if conceived by an unrestrained imagination; odd and remarkable; bizarre; grotesque

fantastic rock formations; fantastic designs.

fanciful or capricious, as persons or their ideas or actions

We never know what that fantastic creature will say next.

imaginary or groundless in not being based on reality; foolish or irrational

fantastic fears.

extravagantly fanciful; marvelous.

incredibly great or extreme; exorbitant

to spend fantastic sums of money.

highly unrealistic or impractical; outlandish

a fantastic scheme to make a million dollars betting on horse races.

Informal . extraordinarily good

a fantastic musical.

adjective

fancy , fantastic , imaginative , whimsical , chimeric , chimerical , conceptual , fanciful , notional , unreal , visionary , changeable , erratic , fickle , freakish , inconsistent , inconstant , mercurial , temperamental , ticklish , uncertain , unpredictable , unstable , unsteady , variable , volatile , amazing , astonishing , astounding , incredible , marvelous , miraculous , phenomenal , prodigious , stupendous , unbelievable , wonderful , wondrous , antic , bizarre , far-fetched , grotesque , fictional , fictive , invented , made-up , divine , fabulous , glorious , sensational , splendid , superb , terrific