This is a minor pet-peev area of mine.
To me you are only a swinger if you are in a commited relationship and exchange/invite extra partners for sex.
I don't think intercourse is required but its gotta be more than heavy petting.
So singles are not swingers, none of the flirty couples are swingers, some guy bringing a call girl isn't a swinger, married but not to each other couples, are again, not swingers, nor do I feel open marriages make you a swinger.
Maybe my definition seems narrow but some make it so broad as to become meaningless. If you get off on your wife going to a bar alone, picking up some guy, and then telling you about it, thats fine, but its not something my wife or I could relate to nor would I call it swinging. If you are a single guy that for whatever reason persues couples looking for a MFM, thats great, but you aren't a swinger you are a single guy.
Some seem to get offended by this, and I'm not sure why. Its not saying you shouldn't do what you are doing, its just that the term 'swinger' doesn't apply.
Finally the whole 'lifestyle' thing. To me lifestyle couples would be the ones who's entire social calander seems to revolve around swinging events/parties/etc. Its hard to describe where that line is, but at one point we crossed it, decided it wasn't all that fun, and pulled back. I think most just use it as a euphamism for swinging, but I suppose I reseve it for those who are REALLY into swinging and being seen.