Learner's definition of LUNACY
[noncount]
1
a : extreme foolishness愚蠢 b : something that is very foolish愚蠢的事 -
Quitting her job was lunacy.她辭去工作真是愚蠢。
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It would be lunacy [=madness] to try driving home in this storm.想在這樣的暴風雨中開車回家真是瘋了。
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His idea was considered total/sheer/complete lunacy.大家認爲他的想法十分荒謬。
2
old-fashioned : extreme mental illness : insanity精神錯亂