hmmm, good question, but I'm not sure I'd call it a BS thread. To quote a great Celtci Music website (Ceolas).

"The term 'celtic music' is a rather loose one; for the purpose of Ceolas, it covers the traditional music of the celtic countries - Ireland, Scotland, Wales, Brittany (in France), Galicia (in Spain) and areas which have come under their influence, such as the US and the maritime provinces of Canada, as well as some newer music based on the tradition from these countries. "

I would argue that the term Celtic Music can be generally applied to describe folk and modern songs emerging from Celtic cultures.