When you overprocess something, you do too much to it, especially when you are making food or using a computer.
Overprocessing can be bad because it can change things in a way that is not good.
Examples:
She overprocesses the dough and it becomes too sticky.
The computer overprocesses the data and it takes a long time.
I don't want to overprocess the vegetables and make them too mushy.
He overprocesses the photo and it looks strange.
The machine overprocesses the paper and it tears.
They overprocess the music and it sounds weird.