The words Mad and bald put together. Someone who is Mald is either a mad and bald person, or a person who is Mad about being bald, and is therefore taking their frustration out on others.
Mike: Ha! Nice hair bro
John: Dude shut up, they shaved my head while I was sleeping you should have stopped them.
Mike: Why are you blaming me for you having too many drinks and passing out? You're so Mald.