Both men continually bad-mouthed each other.

两个男人继续彼此诽谤。

That insidious man bad mouthed me to almost everyone else.

那个阴险的家伙几乎见人便说我的坏话。

I thought she was my best friend. Then she went and bad mouthed me in front of my boyfriend.

我原把她当我最好的朋友，但她却跑到我男朋友那里说我的坏话。

Then she went and bad mouthed me in front of my boyfriend.

我原把她当我最好的朋友，但她却跑到我男朋友那里说我的坏话。

Having a little tiff, they bad mouthed each other.

他们有个小争执，彼此谩骂。