Pronunciation: (lOO'nu-sē), [key]
1. insanity; mental disorder.
2. intermittent insanity, formerly believed to be related to phases of the moon.
3. extreme foolishness or an instance of it: Her decision to resign was sheer lunacy.
4. Law.unsoundness of mind sufficient to incapacitate one for civil transactions.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.