A more thorough explanation:

Definition: Incurable Insanity is a legal grounds for obtaining a divorce under family law. It means that one spouse is so mentally impaired that they do not understand what they are doing or the consequences of their actions.

For example, if a spouse has a severe mental illness that causes them to act in dangerous or harmful ways, and they are unable to receive treatment or improve their condition, their partner may seek a divorce on the grounds of incurable insanity.

However, it is difficult to prove both the insanity of the spouse being divorced and that the insanity is incurable. Therefore, this legal grounds for divorce is rarely used.