I think I know it when I see them (at least some of the time -- there might be more of them that I'm not noticing), but I can't think of a good intensional description of them (and it doesn't seem polite to me to point at extensional examples based on actual people, even in anonymized form).

It probably also depends on what common knowledge exists or does not exist among the two of you, incl. what culture you're in.