のいないところで悪口を

badmouth someone behind their back

→ の
phrase Rare #41,852
badmouth someone behind their back Usually followed by 言う, as in のいないところで悪口を言う. The phrase literally means “in a place where someone is not,” but it is used for speaking badly about someone when they are absent.
JA: 友達のいないところで悪口を言うのはやめよう。
EN: Let's stop badmouthing our friends behind their backs.

その人のいないところで悪口を言ってはいけない

You shouldn't speak ill of someone behind their back.

相手のいないところで悪口を言うな

Don't badmouth people behind their backs.

のいないところで悪口を言わないで下さい

Please don't bad-mouth people behind their backs.

ジムのいないところで悪口を言ってはいけない

You mustn't speak ill of Jim behind his back.