The phrase "lives off" refers to when someone relies on someone else or something else for their livelihood or sustenance. There are several synonyms for this phrase such as "survives on," "feeds off," "exists on," "depends on," "subsists on," and "draws sustenance from." These synonyms are commonly used when describing situations where someone needs the support of something else to get by. For instance, a person may "depend on" their partner's income to get by, or "subsist on" a strict diet due to medical restrictions. These phrases can help convey the idea of dependence and reliance on external factors for day-to-day living.