There are various synonyms for the phrase "keep your trap shut," which means to keep quiet or stop talking. Some of the common ones include "zip it," "button your lip," "shut your pie hole," "stay silent," "keep mum," "don't blabber," "halt the chatter," "cease the noise," "quell your tongue," and "keep your mouth closed." These phrases are often used in informal settings to ask someone to be quiet, especially when they are being rude or talking out of turn. It is important to use these expressions thoughtfully and respectfully to avoid offending others.