This lesson brought back some old lessons in metaphysics. Aristotle wrote in Categories about the different ways of being. The categories seem to be a suitable test for concreteness of concept. While I have not exhaustively tested for completeness, it might do for a rough guide.
Aristotle's Ten Categories are:
We can't really apply these categories to abstract concepts -- but we can to concrete things. That's what makes it a good test to measure for concreteness and specificity.
Take, for example, the word "kiss." Is "kiss" an abstract or concrete concept?