na-adjective, noun
absurd; nonsensical; preposterous
Describes ideas, stories, or claims that are wildly illogical, baseless, or contrary to common sense. Often used in critical or dismissive contexts.
彼の説明は荒唐無稽で、誰も信じなかった。
His explanation was so absurd that no one believed it.
その小説の筋書きは荒唐無稽だが、面白い。
The plot of that novel is preposterous, but it's interesting.