Imagine a situation where a person has needlessly been injured by another.
想象一下，如果一个人毫无理由地被另一个人弄伤了。
The injured person is naturally hoping for some help.
这个受伤的人自然希望得到一些帮助。
Instead, the cruel one who injured that person starts shouting terrible, insulting words.
但是恰恰相反，这个冷漠的人还向这个受伤的人大声恐吓，说一些侮辱性的话。
Thus, the victim has now been injured both physically and emotionally.
结果，受害人身体上和心理上都受到了伤害。
It is a kind of double injury, making an already bad situation become worse.
这是一种双重伤害，使本已糟糕的情况变得更糟。

Now, to use this expression as an idiom, there has to be a situation in which something bad caused by another person becomes worse because of them.
这种表达方式作为一个成语来使用，是指某人在做出糟糕的事后把情况弄得更糟。
There need not be any actual physical injury, and no one may actually be speaking insulting words.
在这种情况下，不一定造成什么身体伤害，也不一定有什么侮辱性的语言。
However, it is clear someone feels injured in some way, and that injury is being increased, not lessened.
但是，的确有人因某种方式受到了伤害，而且伤害还加重了，一点没有减少。
For example, if a friend breaks your favorite dish, that is a kind of first injury.
例如，如果有朋友打翻了你最爱的碗碟，你会感到伤心。
If that friend then criticizes you for having cheap, easily broken dishes, that is adding insult to injury.
但是如果那个朋友接着讽刺你专买那些便宜的和容易破碎的碗碟，这对你而言可就是雪上加霜了。