An idiom meaning to make someone's pain or misfortune worse by words or actions (literally, rubbing salt into a wound).
失恋した友人に新しい恋人の話をわざわざするなんて、まるで傷口に塩を塗るようなものだ。
Telling a heartbroken friend about your new partner on purpose is like rubbing salt in the wound.
試験で落ちたのに先生が点数を比較して笑ったので、傷口に塩を塗られた気分だった。
I failed the exam, and the teacher compared scores and laughed — it felt like salt in the wound.
病状が良くなりかけていた母に冗談で悪化した話をするのは、本当に傷口に塩を塗る行為だ。
Joking about her condition worsening when my mother's health was improving is truly rubbing salt in the wound.