250二百五 (rbǎiwǔ) a careless or silly person

The phrase “二百五 (èrbǎiwǔ)” refers to people who are silly, innocent and careless. Though this word is a little negative, it is commonly used in daily life. Sometimes, instead of sincerely trying to insult someone, it is used as a friendly way to comment on people who don’t think or do things carefully. Now, many people also shorten it as “二 (èr),” which is used as an adjective or adverb. To be honest, I don’t like this word. In my opinion people who say this often is a mean person.
Example:
Lǐ Léi: Nǐ gēn  nǐ jiě zhǎng de hǎo xiàng a.
李雷： 你 跟 你 姐

长 得 好 像 啊。
Li Lei: Jon, you look very much like your sister.
Qiáoēn: Nǐ ge èrbǎiwǔ, zhèshì wǒ mā.
乔恩 ： 你 个 二百五，这是 我 妈。
Jon: You got the cabbage head. This is my mother.