There are several synonyms for the phrase "out of business." One common term is "closed down," which suggests a permanent cessation of operations. Another synonym is "defunct," which indicates that the company is no longer functioning or operating. "Bankrupt" is another synonym, which implies that the company has gone through a legal process of insolvency. Other phrases that can be used to convey the same idea include "shut down," "ceased operations," or "discontinued." Regardless of the phrasing used, the term suggests that the company is no longer operating or providing services or products to customers.