big box noun 2big-box adjective 1forms 3 noun2 •A large self-service store, usually on a single level, with few interior walls, owned and run by a corporation.Expect major mall owners to step up their courting of discounters and big boxes. — 2006 •[before a noun] Software supplied in a large box made from card, typical of the 1990s. big-box adjective1 •(US) Of or relating to a very large retail establishment built as a massive, free-standing structure.Big-box retailers like Wal-Mart have driven local mom-and-pop stores out of business. formsbig boxes · more big-box · most big-box