expression
don't talk nonsense; stop talking rubbish
A humorous, idiomatic retort meaning 'That's nonsense; you're talking in your sleep.' Literally: 'Say your sleep talk after you go to sleep.' Used to dismiss absurd or unrealistic statements.
「宝くじが当たったら仕事を辞めるよ」「寝言は寝て言え」
"If I win the lottery, I'll quit my job." "Don't talk nonsense."
そんな無理な計画、寝言は寝て言えだよ。
That impossible plan is just nonsense.