What is the synonym for smart mouth?

There are many synonyms for "smart mouth," depending on the specific context and nuance you want to convey. Here are some options:

Formal:

* Sassy

* Insolent

* Impertinent

* Disrespectful

* Audacious

* Brash

Informal:

* Wiseacre

* Wise guy

* Lip

* Backtalk

* Sass

* Mouthy

More specific:

* Sarcastic (if the person is being sarcastic)

* Argumentative (if the person is prone to arguing)

* Contentious (if the person is argumentative and likes to pick fights)

* Glib (if the person is quick-witted and can talk their way out of anything)

The best synonym to use will depend on the specific situation and the tone you want to convey.