What are you (doing something) about?

Use this expression when someone has an unusual expression or makes a strange noise. You ask this to find out the reason for the action.

What are you smiling about?

What are you frowning about?

What are you barking about?

(a cat) is meowing

In English "Meow!" is how we describe the sound that a cat makes.

You can turn "meow" into a verb by adding "-ing" to the end:

Lucy is meowing. She must be hungry.

This is true for some other animal noises:

The cow is mooing.

The ducks are quacking.

But it doesn't always work. For example, when a dog or a bear is angry, it makes this sound:

Grr!

But there's a special verb for making this sound, which is "growling".