A more thorough explanation:

An equitable defense is a reason given by a defendant as to why the plaintiff's case is not valid. It is a type of defense that was previously only available in a court of equity but can now be used in a court of law. Examples of equitable defenses include mistake, fraud, illegality, failure of consideration, forum non conveniens, laches, estoppel, and unclean hands.

For instance, if a plaintiff sues a defendant for breach of contract, the defendant may use an equitable defense of fraud, claiming that the plaintiff misled them into signing the contract. Another example is if a plaintiff sues a defendant for patent infringement, the defendant may use an equitable defense of unclean hands, arguing that the plaintiff breached the duty of candor and good faith during the patent prosecution.

Equitable defenses are used to prevent the plaintiff from recovering what they seek in their complaint or petition. They are important in ensuring that the legal system is fair and just for all parties involved.