Chinese characters 倒 dǎo, “upside down”, or “reverse”, actually can be used in all kinds of interesting ways. With the meaning of “reverse”, it can be placed between a two character word to reverse the meaning of that word.
The best way to understand this is to look at some examples.
Let’s say, “帮忙 bāngmáng” means “to help”. What if your four year old wants to help you with some difficult chores that not only he couldn’t help, but also needs your help to tidy up after his “helping”? For that kind of situation, you can say your child is “帮倒忙 bāngdàománg“.
Now let’s look at another example. People usually applaud or even give standing ovation to marvelous performance. In Chinese, this kind of reaction from the audience is called “喝彩 hècǎi“. What if the performance ends up the opposite way? Audience might start booing. In that case, we can use 倒 dǎo between 喝 hè and 彩 cǎi, which becomes 喝倒彩 hèdàocǎi.
Do you get it? Do you know any other word that you can use it this way?