1.
If you say that someone keeps open house , you mean that they welcome friends or visitors to their house whenever they arrive and allow them to stay for as long as they want to.
Father Illtyd kept open house and the boys would congregate in his study during their recreation time, playing cards or games.
N-UNCOUNT
2.
An open house is a day on which members of the public are encouraged to visit a particular institution or place to see what it is like. ( AM; in BRIT, use open day )
A week later, Sara and I attended open house at Ted’s school...
N-VAR : also N n