Mitotic catastrophe is like when you are playing with building blocks and you try to build a tower that is too tall and it falls down, making a big mess. In cells, when they divide, they also try to make copies of themselves, but sometimes things go wrong and they can't finish the job properly.
This can happen when the cells are damaged, during radiation or chemotherapy treatments, or because of genetic problems. When the cells can't complete the process of dividing properly, they can't make two healthy cells, instead they create a lot of cells that are all messed up.
These cells can cause chaos and harm to the body's tissues. Imagine if you had a bunch of blocks that were all broken and couldn't really stack properly. You wouldn't be able to build anything that looks like a proper tower, and instead, you would have a pile of blocks that didn't work properly.
The same thing happens in your body when the cells can't finish dividing correctly. This is called mitotic catastrophe, and it can be really harmful to your health. Scientists are studying this process to try and find ways to help prevent or treat diseases that happen because of this problem.