1. extreme foolishness or an extremely foolish act
2. mental illness or insanity
Usage: dated; potentially offensive

Examples

• It would be sheer lunacy to drive in this blizzard.
• The committee called the proposal financial lunacy.
• His decision to quit his job without another lined up seemed like lunacy to his friends.
• The lunacy of the plan became apparent when they ran out of money.
• She thought it was lunacy to spend so much on a wedding.
• The coach’s strategy was dismissed as pure lunacy by the sports commentators.