What is the meaning of this idiom By word mouth?

The idiom "by word of mouth" is actually "by word of mouth" and it means spread by people talking about it to each other, rather than by advertising or other means.

Here are some synonyms:

* Through the grapevine

* Word of mouth

* Oral communication

* Informal communication

Here are some examples of how the idiom is used:

* "The restaurant is getting a lot of business by word of mouth."

* "News of the protest spread by word of mouth."

* "The rumor about the celebrity's marriage spread by word of mouth."

The idiom is often used to describe how information spreads quickly and informally within a community. It can also be used to emphasize the authenticity of the information, as it is coming directly from people who have experienced it firsthand.