Definition
To exacerbate an already unpleasant situation, making it even more distressing or painful for someone.
It was bad enough that she was fired, but him constantly bringing up her mistakes was like rubbing salt in the wound.
Not only did he lose the game, but he also had to watch the opposing team celebrate their victory, which was like rubbing salt in the wound.
When she found out that they had all received promotions, it was like rubbing salt into the wound, as she had missed out on the opportunity herself.