What does "on top of" mean and when's it used?

Native speaker’s answer
Rebecca
"On top of that" is an expression which means "also" or "in addition to." You can use it when you want to add emphasis when you are introducing a new, significant addition to a list. Ex: On top of it raining, I got splashed by a car on the way to work. Ex: I hurt my foot and on top of that, I got stung by a bee!