An expression meaning absurd or preposterous; having no basis in reason or fact.
その話は根拠がなく、荒唐無稽だ。
That story has no basis and is absurd.
彼の言い分は荒唐無稽としか言いようがない。
There is no way to describe his argument except as preposterous.
荒唐無稽な噂がインターネットで広まった。
A preposterous rumor spread on the internet.