I wasn't trying to bad mouth your family. I was only telling my mom what had happened.

我不是想说你家人的坏话！我不过是跟我妈说所发生的事罢了。

youdao

It is bad manners to talk with your mouth full.

嘴里塞满了东西跟人说话是不礼貌的。

《牛津词典》

You always bad-mouth me in front of our manager. What do you want?

你总是在经理面前说我坏话。你想干吗？

youdao

For example, if you say bad things about a person, the person might protest and say "Do not bad mouth me."

VOA: special.2010.06.20

He might say that experience "left a bad taste in my mouth."

VOA: special.2010.06.20

Aside from refusing to ever hire you again, executives have long memories and will bad mouth you any chance they get.

FORBES: Magazine Article

You pause, remind yourself that an employer (via its employees) cannot bad mouth you, breathe a sigh of relief and complete the application.

FORBES: Tips for Tackling a Tarnished Reputation

Since Apple has fallen behind in OLED technology, it makes sense for Apple to bad mouth OLEDs while behind the scenes scrambling to catch up.

FORBES: Tim Cook Does Not Like OLED But Spends Money On It