忍俊不禁 Unable to restrain laughter
Explanation
忍俊不禁的意思是忍不住笑，形容非常可笑。
The idiom "rěn jùn bù jìn" means to be unable to restrain oneself from laughing; it describes something extremely funny.
Origin Story
话说唐朝时期，有个才华横溢的官员，名叫李白。一天，他正与友人饮酒作乐，突然听到窗外传来一阵阵奇怪的叫声。好奇之下，他推开窗户，只见一只肥胖的猫正倒挂在树枝上，拼命地挣扎着，模样滑稽至极。李白和友人见状，都忍不住哈哈大笑，笑声震彻庭院。李白的友人指着那只猫说道：‘这猫就像那舞台上的小丑，真是滑稽可笑！’李白听了，也觉得好笑，说道：‘是啊，我真是忍俊不禁啊！’说完，两人又大笑起来，笑声久久不息。这便是‘忍俊不禁’的由来。此后，‘忍俊不禁’便成了人们形容忍不住要发笑时常用的词语，表达了那种发自内心的愉悦和轻松。
It is said that during the Tang Dynasty, there was a talented official named Li Bai. One day, he was drinking and having fun with his friends when he suddenly heard strange noises from outside the window. Curious, he opened the window and saw a fat cat hanging upside down from a tree branch, struggling desperately. Its appearance was extremely comical. Li Bai and his friends couldn't help but burst into laughter, their laughter echoing through the courtyard. Li Bai's friend pointed at the cat and said, 'This cat is like a clown on stage, so funny!' Li Bai also found it funny and said, 'Yes, I can't help but laugh!' After that, they laughed again, their laughter lasting for a long time. This is how the expression "rěn jùn bù jìn" originated. Since then, "rěn jùn bù jìn" has been often used to express being unable to restrain oneself from laughing, expressing heartfelt joy and ease.
Usage
用于描写忍不住笑的情况，多用于口语。
Used to describe situations where one can't help but laugh, mostly used in spoken language.
Examples
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看到他滑稽的表演，我忍俊不禁，笑出了声。
kan dao ta huaji de biaoyan, wo renjunbujin, xiao chule sheng.
I couldn't help but laugh at his funny performance.
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听到这个笑话，我们都忍俊不禁。
ting dao zhege xiaohua, women dou renjunbujin
That joke made us all laugh uncontrollably.