【Fantastic】 ,  【bizarre】 ,  【grotesque】 ,  【antic】  are comparable when they describe works of art, effects produced by nature or art, ideas, or behavior and mean conceived or made, or seemingly conceived or made, without reference to reality, truth, or common sense.

【Fantastic】 stresses the exercise of unrestrained imagination or unlicensed fancy. It therefore variously connotes absurd extravagance in conception, remoteness from reality, or merely ingenuity in devising.

【Bizarre】 is applied to what is unduly, often sensationally, strange or queer; it suggests the use of violent contrasts (as in color, in sound, or in emotional effects) or of strikingly incongruous combinations (as of the tragic and the comic or of the horrible and the tender).

【Grotesque】 emphasizes distortion of the natural to the point either of comic absurdity or of aesthetically effective ugliness. Technically the word is applied to a type of painting or sculpture of ancient Roman origin which serves a decorative rather than a pictorial purpose and which employs natural details (as animals, men, flowers, and foliage) and conventional designs and figures (as scrolls, garlands, and satyrs) in unnatural combinations or to the comic exaggerations or distortions of human and animal figures in the sculptured decorations and especially the gargoyles of Gothic architecture. It is from the latter association that the adjective in general use derives its leading implications of ridiculous ugliness or ludicrous caricature.

Sometimes the word suggests an absurdly irrational combination of incompatibles.

【Antic】 , chiefly in literary use, though once indistinguishable from  【grotesque】 , has come to stress ludicrousness or buffoonery more than unnaturalness or irrationality.