The adjective implausible means something you believe that is unlikely to be true.

Synonyms are dubious, far-fetched, impossible, or inconceivable.

The word origins from 1670s. It comes from in– meaning “not, opposite of” plus plausible. In the past, it meant “not worthy of praise”.

She found it implausible when she visited a psychic to solve her problems.

The complainant’s story seems implausible at first.

Does it all sound utterly implausible for you?