Sentence:  For the occasion on which everyone already knows everyone else and the host wishes them to meet one or a few honored newcomers , then the `` <WSD>open</WSD> house '' system is advantageous because the honored guests are fixed connective points and the drifting guests make and break connections at the door . 
Meaning of the word marked with <WSD> tags:  an informal party of people with hospitality for all comers