This is a common expression we use in English to mean that someone is at a bad point in their life.
The Definition is: To reach the lowest point, or level. Or, to be in a really bad situation.
Last year I lost my job, my house, and my wife left me. I really hit rock bottom.
The company has hit rock bottom. The only thing left to do is close.
Basically, if you get to this stage in your life you need to change something quick smart.
Here's another English expression for you to learn.
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