A Defamation Act is a law that makes it against the law to say or write mean and false things about another person. This law is designed to keep people from making hurtful and untrue statements about someone else. For example, if you said that your neighbor was a thief, and it wasn't true, that could be considered defamation and would break the law. If someone was found guilty of breaking the Defamation Act, they could get in trouble with the police and even have to pay a penalty.