use of "bad mouth"

English as a Second Language English Vocabulary, Grammar and Idioms
1

Please let me know if it’s grammatically correct:

  1. Just because I committed one mistake that doesn’t mean you should bad mouth about me to others.
2

…doesn’t mean you should bad mouth me to others. (informal)

3

I thought ‘badmouth’ all in word.

4

As it’s informal slang I don’t believe I’ve ever seen it written down before, but I would never consider it to be one word. Google has both - perhaps we can compromise by hyphenating it, as this seems to be the most common form:
bad-mouth
bad-mouthing
idioms.thefreedictionary.com/bad-mouth

5

Thank you for your explanation.

6

Had a question why aren’t we using “bad mouth about me” and why just “bad mouth me”? What is the reason of not using “about”? Please explain. thanx

7

It’s idiomatic, Hardwork. The ‘about’ isn’t specifically needed because it is included within the meaning of the idiom:
‘bad mouth’ = ‘say unpleasant things about’
therefore
‘bad mouth about’ would be equivalent to saying ‘say unpleasant things about about’.

8

So is this correct

  1. She was bad mouthing you
9

Yes. “She was saying unpleasant things about you.”