noun
lunacy
LOO-nuh-see
noun
1
Madness or insanity, especially of a kind once believed to come and go with the phases of the moon.
"His wild rants were dismissed as lunacy by everyone who knew him."
2
Something reckless or deeply misguided, without necessarily involving actual mental illness.
"Driving in that storm would be pure lunacy."
"Spending the whole budget on one advert was lunacy."
How to Use Lunacy
Learner’s notesIn plain EnglishMadness — either literal insanity or, more commonly today, just a wildly reckless or foolish idea.
Common pairings
sheer lunacy
an act of lunacy
Word Forms
lunacies plural
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Etymology
From lunatic + the noun-forming suffix -cy; ultimately from Latin luna ("moon"), reflecting the old belief that madness waxed and waned with the moon.