""I think the problem here is that we keep using the word 'definition' for something which can't be defined."
It can and has been defined - what can't be defined is what is happening at folk clubs today."

You've missed my point, that is exactly what I was saying. Nevertheless, although what happens in folk clubs can't be pinned down to a definition, there is a widely understood understanding of what you can expect to hear. This is of course very fuzzy around the edges and no clear lines can be drawn.

I am also saying that what you understand as 'folk' can be defined, indeed this is what in objective terms makes it distinctive. However your insistence that any other meaning is wrong may be technically correct but flies in the face of common usage. Your view that this other meaning is not understood by the "man in the street" flies in the face of common experience.