Mal de coucou is a phenomenon in which you have an active social life but very few close friends—people who you can trust, who you can be yourself with, who can help flush out the weird psychological toxins that tend to accumulate over time—which is a form of acute social malnutrition in which even if you devour an entire buffet of chitchat, you'll still feel pangs of hunger.
Mal de coucou指社交活动很丰富但是没什么亲近好友的现象，没有你可以信任的人，没有可以展现真实自我的人，没有可以倾诉长期积压的内心苦水的人。这种现象属于严重的社交营养不良，就好像你跟人天南海北聊了一天，仍然渴望有人跟你说说话。
This expression is a loan term from French, in which coucou is an informal reference to a close friend, while mal means pain of inadequacy of something.
这个表达来自于法语，coucou是对亲密朋友的非正式称呼，mal则指痛苦或缺失。总体来说，我们可以把mal de coucou理解为“好友缺失症”。
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