fanciful

1. ADJ If you describe an idea as fanciful, you disapprove of it because you think it comes from someone's imagination, and is therefore unrealistic or unlikely to be true. 異想天開(kāi)的[表不滿(mǎn)]

...fanciful ideas about Martian life. …關(guān)于火星生命的異想天開(kāi)。