信口雌黄

晋朝时，有个名叫王衍的名士，特别擅长清谈。有一次，他跟朋友们聚在一起闲聊，谈论起老庄的哲学思想。他侃侃而谈，引经据典，然而言辞却前后矛盾，漏洞百出。有人指出他的错误，他就立刻修改说法，张口就来，毫不脸红。人们因此称他为“口中雌黄”，意思是说他说话不顾事实，随口乱说。

jìn cháo shí, yǒu gè míng jiào wáng yǎn de míngshì, tèbié shàncháng qīngtán. yǒu yī cì, tā gēn péngyǒumen jù zài yīqǐ xiánliáo, tánlùn qǐ lǎo zhuāng de zhéxué sīxiǎng. tā kǎnkǎn értán, yǐn jīng jù diǎn, rán'ér yáncí què qián hòu máodùn, lòudòng bǎichū. yǒurén zhǐ chū tā de cuòwù, tā jiù lìkè xiūgǎi shuōfǎ, zhāng kǒu jiù lái, háo bù liǎn hóng. rénmen yīncǐ chēng tā wèi "kǒu zhōng cí huáng", yìsi shì shuō tā shuōhuà bù gù shìshí, suí kǒu luàn shuō.

During the Jin Dynasty, there was a famous scholar named Wang Yan who was particularly skilled in casual conversation. Once, he gathered with friends to chat about the philosophical thoughts of Laozi and Zhuangzi. He spoke eloquently and quoted classics, but his words were contradictory and full of loopholes. When someone pointed out his mistakes, he immediately changed his statement, speaking freely and without blushing. Therefore, people called him "oral ci huang", meaning that he spoke without regard to the facts.

信口雌黄通常作谓语、宾语和定语，用来形容说话不负责任，不顾事实，随意乱说。

xìn kǒu cí huáng tōngcháng zuò wèiyǔ, bǐnyǔ hé dìngyǔ, yòng lái xíngróng shuōhuà bù fù zérèn, bù gù shìshí, suíyì luàn shuō

The phrase "信口雌黄" usually acts as a predicate, object, and attributive, describing an irresponsible and reckless way of speaking without considering facts.