An antonym for the phrase "shot off one's mouth" can vary depending on the context of the situation. However, some possible antonyms may include "kept quiet", "listened attentively", "remained reserved", "exercised restraint", or "maintained composure". These antonyms highlight a tendency for individuals to control their emotions, hold their tongue, and refrain from making rash or inappropriate comments. In certain situations, it may be wise to act in opposition to the phrase "shot off one's mouth" to avoid negative consequences, maintain relationships, or preserve one's reputation. Thus, it is important to consider the appropriate antonym based on the particular context of the situation.