open house

noun5

1. •
   An event, often in one's home, at which there are few restrictions regarding who and how many may attend.
2. •
   An event during which a facility or institution is open to the public for inspection or tour.
3. •
   (US, 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.
4. •
   (US) A casual school event where the school invites parents or guardians to tour their child's school and meet the teachers before the school year begins
5. •
   A house habitually kept open to callers.

   • He keeps a kind of open house for all the respectable young men of the town who are staying in lodgings. — 1839