In the Chinese idiom (成语) xinkou cihuang, what does cihuang mean?
The Chinese. idiom xinkou cihuang refers to someone speaking out in an irresponsible(不负责任的)way. Cihuang is a kind of mineral (矿物). In the past, for some time, people in China used yellow. - colored paper. Cihuang is about the same color. So when people wanted to correct(纠正)something on paper, they used cihuang.
There is a story behind the idiom. Wang Yan was an official(官员) during the Western Jin Dynasty. He liked talking about philosophy(哲学). But his ideas were often wrong. People sometimes pointed this out to Wang. But he didn't think it was a big problem. He'd just correct himself and go on like nothing happened. So people started to call him xinkou cihuang. The idea is that Wang always kept a piece of cihuang in his mouth so that he could correct anything he had just said.