Meaning:

“嘴” means “mouth,” and “替” is short for “替身” (tìshēn: meaning “someone’s double,” such as a stuntman for a star in a movie). This term, coined by Chinese netizens, is used to refer to someone who speaks out the exact words other people want to say, such as the straightforward celebrities who make impressive observations on talk shows or those who leave to-the-point comments under a post on social media. Therefore, if someone tells you that you are their “嘴替,” you can take it as a compliment meaning “I can’t agree more.”

Example:

A: 这个女嘉宾就是我的互联网嘴替。

Zhè ge nǚ jiābīn jiùshì wǒ de hùliánwǎng zuǐtì。

This woman guest on the show has spoken my mind.

B: 可不是嘛，现在普信男太多了。

Kě búshì ma， xiànzài pǔxìnnán tài duō le。

Isn’t it true! There are so many men who just feel too good about themselves.