It's incorrect to say it's "undefined" which means "without definition". The "problem" is that it has a "fuzzy definition", or you could rightly claim "multiple

It's incorrect to say it's "undefined" which means "without definition". The "problem" is that it has a "fuzzy definition", or you could rightly claim "multiple definitions", depending on the context. But, a good definition must come after understanding, not before. And, just because something doesn't have a precise definition or understanding doesn't mean that understanding can't be improved, or even branched, in the form of a discovery, to create some new label that better fits the concept. Until then, we have to live with something fuzzy, with the understanding that it is somewhat incorrect (which anyone familiar with biology will happily tell you). Lack of definition, which is lack of understanding, doesn't impede discovery. Lack of definition and understanding are necessary requirements for discovery.