o·pen house • n. a place or situation in which all visitors are welcome: they kept open house, entertaining a wide variety of artists and writers. ∎ a day when members of the public are invited to visit a place or institution, esp. one to which they do not normally have access: the president spent all morning greeting thousands of visitors to a White House open house. ∎ an informal reception or party during which one's home is open to visitors: on New Year's Day they had an open house. ∎ a time when real estate offered for sale is open to prospective buyers.