Definition schmefinition. Our club in Exmouth uses the appelation Folk night.I have found it hard at open Mics inviting people to come to the event because they don't believe they are folky enough. Theyb are not using gtheir own definition, rayher an assumed identity projected by others. I now use the term acoustic night as often as 'folk' just so people don't get put off. A typical night will include a shanty crew, an acoustic band playing english/irish tunes, a couple of unaccompanied traddies, some blues, a couple of singer/songwriters, some appalachian stepping to fiddle accompaniment,a young man of 17 playing hendrix and pink floyd covers, a veteran of the fifties playin rock n roll and some groups or individuals playing mainly trditional stuff to instrumental accompaniment. Sometimes we also get a close harmony group. Not a microphone in sight, and intense listening and appreciation.
    Basically 'folk' to us means anything that you can get up and do without technology, that people can enjoy and perhaps join in with and owes some debt to ordinary music of the people ( not necessarily Folk of the ( non-folk) elite).
    Just like it was when I first went to clubs in the sixties when there was an eclectic mix of contempoorary American, blues, sea songs,Irish rebel songs, a few unacompanied traditional singers, ragtime and singer sogwriters. There was a time when 'traditional'became de riguer, which was fine for those like me who love that style, but it meant a generation seeing 'folk'as stuffy and not to do withy them. The new generation have joined back inn to reclaim mlive acoustiv music, so our folk nights have performers representing each decade from teens to octogenarians. All the folk, not just some.