The definition of lunacy is the state of being insane or wild foolishness.
An example of lunacy is college students and intense partying over Spring break.
- Obs. intermittent insanity, formerly supposed to change in intensity with the phases of the moon
- mental unsoundness; insanity
- pl. -·cies great folly or a foolish act
Origin of lunacyluna(tic) + -cy
- a. Mental derangement; craziness: “The Indians thought his obsession with giant bones a sign of harmless lunacy” ( David Rains Wallace )b. Archaic Intermittent mental derangement attributed to the changing phases of the moon.
- a. Great or wild foolishness: a policy that proved to be a piece of economic lunacy.b. A wildly foolish or irrational act.
Origin of lunacyFrom lunatic
(countable and uncountable, plural lunacies)
From lunatic + -cy.