Worthless, trivial, or not worth bothering about — a dismissive way to say something is insignificant.
そんなくだらんことに時間を使うな。
Don't waste time on such trivial things.
彼の言うことはほとんどくだらん冗談だ。
What he says is mostly worthless jokes.
くだらん理由で会議が延びた。
The meeting was extended for a trivial reason.
Stupid, nonsensical, or absurd — used to criticize something as foolish or ridiculous.
そんなくだらん考えで人を傷つけてはいけない。
You mustn't hurt people with such a foolish idea.
彼女の説明は筋が通らず、みんながくだらんと言った。
Her explanation made no sense and everyone called it nonsense.
くだらん冗談はやめてくれ。
Cut out the stupid jokes.