What does the idiom sitting on top of world mean?

The idiom "sitting on top of the world" means to feel extremely happy, successful, and content. It implies a feeling of being at the peak of happiness and satisfaction with life.

Here are some other ways to express this feeling:

* On cloud nine: A state of extreme happiness.

* Walking on air: Feeling very happy and lighthearted.

* Over the moon: Very happy and excited.

Example:

"After finally landing that dream job, she was sitting on top of the world."