Chimerical, a.
Merely imaginary; fanciful; fantastic; wildly or vainly conceived; having, or capable of having, no existence except in thought; as, chimerical projects.
Syn. -- Imaginary; fanciful; fantastic; wild; unfounded; vain; deceitful; delusive.
Shades of meaning
Fernald has no entry of its own for chimerical; he lists it under absurd, fanciful.
He lists it without comment; the entries above explain its neighbors.