The antonyms for the phrase "sits out" include "participates," "joins in," "takes part," "engages," and "enters into." These words are used to describe someone who is actively involved in a particular activity or event, rather than sitting on the sidelines. When you participate in an activity, you are taking an active role and contributing to the overall outcome. In contrast, when you sit out, you are choosing not to participate, which can lead to missed opportunities or a feeling of being left out. Therefore, it is important to evaluate whether you want to sit out or engage in a particular activity before making a decision.