Antonyms for the phrase "letting hang out" could include terms such as "covering up," "hiding," "concealing," or "keeping hidden." These antonyms imply a sense of restraint or discretion, indicating that an individual or group is not willing to expose or reveal something openly. In contrast to "letting hang out," these antonyms suggest a sense of containment, privacy, or secrecy. They may be used in a range of contexts, from personal relationships to professional interactions, to describe different approaches to communication, self-expression, or transparency. Ultimately, the choice of antonym will depend on the specific meaning and usage of "letting hang out" in a given context.