不苟言笑 grave and unsmiling
Explanation
苟：苟且，随便。不随便说笑。形容态度庄重严肃。
Gǒu: casual, perfunctory. Does not casually talk and laugh. Describes a solemn and serious attitude.
Origin Story
年轻的书生李文，初次拜访名满天下的大学问家程先生。程先生家简朴，院中一棵古柏，枝繁叶茂。李文屏气凝神，来到书房，只见程先生正伏案批阅卷宗，不苟言笑。李文不敢打扰，只轻轻地放下拜帖。程先生头也不抬，只嗯了一声，继续批改。李文静静地站着，心中忐忑，却又敬佩程先生的认真态度。许久，程先生才抬起头，目光如炬，上下打量着李文。李文更加紧张，结结巴巴地介绍来意。程先生听后，沉默片刻，说：‘请坐下，我们慢慢谈。’ 程先生的专注和认真，让李文体会到读书人的境界，从此更加努力学习，潜心治学，最终也成为一方名士。
The young scholar Li Wen paid his first visit to Mr. Cheng, a renowned scholar. Mr. Cheng's house was simple, with an old cypress tree in the yard, lush and full of branches. Li Wen entered the study with bated breath. Mr. Cheng was at his desk, reviewing documents, his expression serious. Li Wen dared not disturb him, just gently put down his visiting card. Mr. Cheng didn't lift his head, only humming. Li Wen stood quietly, his heart pounding, yet admiring Mr. Cheng's seriousness. After a long time, Mr. Cheng lifted his head, his eyes bright, examining Li Wen. Li Wen became even more nervous and stammered to explain his purpose. Mr. Cheng listened, silent for a moment, and said: 'Please sit down, let's talk slowly.' Mr. Cheng's focus and seriousness made Li Wen understand the realm of a scholar. From then on, he studied even harder and eventually became a famous scholar himself.
Usage
作谓语、定语；形容表情庄重、严肃
Used as predicate or attributive; describes a solemn and serious expression.
Examples
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他为人严肃认真，不苟言笑。
tā wéirén yánsù rènzhēn, bù gǒu yán xiào
He is serious and earnest, never smiling.
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会议上，领导不苟言笑，气氛凝重。
huìyì shàng, lǐngdǎo bù gǒu yán xiào, fēnwéi níngzhòng
At the meeting, the leader was serious and the atmosphere was solemn.
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他平时不苟言笑，但内心却很善良。
tā píngshí bù gǒu yán xiào, dàn nèixīn què hěn shànliáng
He is usually unsmiling, but he is kind at heart.