Etymology: Middle English fantastic, fantastical, from Middle French & Late Latin; Middle French fantastique, from Late Latin phantasticus, from Greek phantastikos producing mental images, from phantazein to present to the mind — more at fancy
Date: 14th century
a. based on fantasy ; not real
b. conceived or seemingly conceived by unrestrained fancy
c. so extreme as to challenge belief ; unbelievable; broadly exceedingly large or great
2. marked by extravagant fantasy or extreme individuality ; eccentric
3. (fantastic) excellent, superlative <a fantastic meal> • fantasticality noun • fantasticalness noun Synonyms: fantastic, bizarre, grotesque mean conceived, made, or carried out without adherence to truth or reality. fantastic may connote unrestrained extravagance in conception or merely ingenuity of decorative invention <dreamed up fantastic rumors to spread>. bizarre applies to the sensationally queer or strange and implies violence of contrast or incongruity of combination <a bizarre medieval castle built in the heart of a modern city>. grotesque may apply to what is conventionally ugly but artistically effective or it may connote ludicrous awkwardness or incongruity often with sinister or tragic overtones <grotesque statues adorn the cathedral> <though grief-stricken, she made a grotesque attempt at a smile>. Synonym: see in addition imaginary. II. noun Date: 1598 eccentric 2
New Collegiate Dictionary. 2001.