It’s a mad, mad world!

It’s a mad world means that it’s a crazy or absurd world.

Indeed, mad is an adjective that has several different meanings.

It can mean to be mentally ill:

The artist went mad in his old age.

or very foolish:

You must be mad to turn down such a good job.

Or very enthusiastic about something or someone:

He’s mad about football.

Or, like the girl in the photo, to be angry:

She was so mad with her sister that she refused to speak to her.