Meaning:
“嘴” means “mouth,” and “瓢,” which literally refers to “a gourd dipper,” can mean “uneven” and “crooked.” In northern Chinese dialect, to say someone has a “crooked mouth” implies that the person talks nonsense, is loudmouthed or has a slip of the tongue.
Example:
A: 你会不会有时候说错话？
Nǐ huìbuhuì yǒushíhòu shuōcuòhuà？
Do you sometimes say the wrong words?
B: 当然会。昨天下午我男朋友看足球比赛，从冰箱里拿出一罐啤酒，我忍不住说他，结果就嘴瓢了。我说：“为什么看酒时一定要喝球呢？”
Dāngrán huì。Zuótiān xiàwǔ wǒ nánpéngyou kàn zúqiú bǐsài， cóng bīngxiāng lǐ náchū yīguàn píjiǔ，wǒ rěnbuzhù shuō tā，jiéguǒ jiù zuǐpiáo le。Wǒ shuō ：“wèishénme kànjiǔ shí yīdìng yào hēqiú ne？”
Of course I do. Yesterday afternoon, when my boyfriend was about to watch a soccer game, he took a can of beer from the fridge. I couldn’t help complaining a bit, but had a slip of the tongue. I said, “Why is it necessary to drink football while you watch beer?”