Meaning:

    “嘴” means “mouth,” and “欠” means “lacking.” Here “欠” is short for “欠抽,” which means “asking for a slap in the face.” A term from old Beijing dialect, it is used to refer to people who are mean with their words and always say things offensive to others.

    Example:

    A: 昨天我的同桌又向老师告状了。

    Zuótiān wǒ de tóngzhuō yòu xiàng lǎoshī gàozhuàng le。

    Yesterday my deskmate complained to the teacher about me again.

    B: 你怎么得罪她了？

    Nǐ zěnme dézuì tā le?

    What did you do?

    A: 她忘了带语文课本。

    Tā wàng le dài yǔwén kèběn。

    She forgot to bring her Chinese textbook.

    B: 那是她自己粗心大意，不关你事啊。

    Nà shì tā zìjǐ cūxīn dàyì, bù guān nǐ shì a。

    She was just so careless, but it’s not your fault.

    A: 我嘴欠，说了句“活该”。

    Wǒ zuǐqiàn, shuō le jù “huógāi”。

    I didn’t control my tongue and said, “Karma.”