"Shoots off mouth" is a colloquial phrase used to describe someone who speaks too quickly or recklessly, often without thinking about the consequences of their words. In contrast, some antonyms for this phrase could be "thinks before speaking," "chooses words carefully," or "speaks deliberately." Other antonyms could include "keeps quiet," "remains silent," or "listens more than talks." Using these antonyms to describe someone's communication style might suggest that they have a more measured approach to speaking, taking time to consider their words and the impact they may have on others.