Definitions
1.nounA house habitually kept open to callers.
2.nounAn event, often in one's home, at which there are few restrictions regarding who and how many may attend.
3.nounAn event during which a facility or institution is open to the public for inspection or tour.
4.noun(Canada and Australia) A period of time, usually several hours in a day, during which a house which is for sale is open for inspection or tour by interested parties."We′re holding an open house this weekend at 77 Parkway Road."
5.nounA casual school event where the school invites parents or guardians to tour their child's school and meet the teachers.