I don't understand. I gave a definition that encompasses the typical way it's used in the relevant biological sciences, you seemingly accepted it ("Biology is OK working that way"--you certainly didn't argue with the definition, anyway), and now you're once again saying it's not well-defined.

Perhaps you mean that it is pretty well-defined, but the distinction between pretty well-defined and not well-defined is unimportant?

As Asimov said, and I agree, "if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together."