disapproval If you describe someone's behaviour as lunacy, you mean that it seems very strange or foolish. the lunacy of the tax system It remains lunacy to produce yet more coal to add to power stations' stockpiles
Insanity or madness; properly, the kind of insanity which is broken by intervals of reason, formerly supposed to be influenced by the changes of the moon; any form of unsoundness of mind, except idiocy; mental derangement or alienation