A sump is a low part in the ground where water collects.
Sumps are usually found in basements or in places where water needs to be removed.
Examples:
The sump in the basement collects water when it rains.
We need to pump the water out of the sump.
The sump is full of water.
The sump is like a big water bowl.
The sump is so full, it's like a swimming pool!
The sump is where all the water goes.