I get the impression that to some people, in the UK at least, a song-circle/singaround is a fairly large group in some sort of commercial venue (such as a pub), in which each person takes a turn singing a song while everyone else listens more or less attentively...that is, there is a performer (who is a moving target) and an audience. In the ones in which I have participated in the US - in several different locations - the locale is usually somebody's living room and it is much more likely to involve group singing than a single singer and a bunch of listeners. Perhaps this is one of the reasons for the very diverse set of opinions.