There are several synonyms for the phrase, "shoot one's mouth off." Some of these synonyms include "spout off," "blabbermouth," "voice one's opinions loudly," "rant," and "chatter incessantly." These synonyms all refer to someone who speaks without thinking beforehand or without considering the consequences of their words. Whether it's speaking out of turn, making rude comments or spreading gossip, shooting one's mouth off can be damaging to relationships, reputations, and careers. It's important to think before we speak and choose our words wisely to avoid these negative consequences.