chimerical. adjective. Unreal; imaginary; of or related to a chimera.

Everyone who has read or watched Fullmetal Alchemist should know what a chimera is. If you don't, it's a monster/creature made up of different parts/animals; the classic Greek one was a fire-breathing thing with a lion's head, a goat's body (and also goat's head sometimes), and a serpent's tail (or a serpent for a tail.

The most basic definition of chimerical (or chimeric) can range from just straight up magical, fantastical or abnormal to more real-world sentiment for things illogical, impractical, or existent only in a fantasy world - stuff like that. If you wanted to use it for a more specific purpose, though, the ideal usage would be for things of a wild, patchwork style similar to a chimera itself, with many different kinds of parts making up the whole. It's a nice, colourful word to consider for writing:

He had a wild, chimerical imagination.
Alec always comes up with these chimerical business plans.
Welcome to the chimeric world of Furi Kuri!

Actually, that said, using chimera alone as a metaphor is great too! something to think about.

(adverb form: chimerically; noun origin: chimera)