noun
plural ~ houses
[count] US :an event in which an organization (such as a school or company) invites the public to visit in order to see the things that happen there
Westside High School will host an open house from 3 to 7 p.m. today, and all parents are invited to attend.
[count] US :an event in which anyone who is interested in buying a particular house, apartment, etc., is invited to go inside and look at it
chiefly Brit :a home or other place in which guests or visitors are welcome [noncount]