“have a big mouth”别理解成“有一张大嘴”，真实含义是嘴巴不严；夸夸其谈；多嘴。

【例句】
I'm sorry, I shouldn't have opened my big mouth.
对不起，我不应该多嘴的。

If you didn't have such a big mouth, I'd tell you my secrets.
如果你不是这么嘴巴不严，我就会告诉你我的秘密的。