- (not in technical use as a medical diagnosis) the condition of being insane; a derangement of the mind.
- such unsoundness of mind as frees one from legal responsibility, as for committing a crime, or as signals one's lack of legal capacity, as for entering into a contractual agreement.
- (formerly) psychosis.
- extreme foolishness: Trying to drive through that traffic would be pure insanity.
- a foolish or senseless action, policy, statement, etc.: We've heard decades of insanities in our political discourse.
- relatively permanent disorder of the mind; state or condition of being insane
- a defect of reason as a result of mental illness, such that a defendant does not know what he or she is doing or that it is wrong
- utter folly; stupidity
