Brainstorming on a workable definition of "Metaphysics"

Metaphysics is a branch of knowledge relating to that which is presently unknowable through a strictly empirical understanding of the universe. It is more related to emerging quantum science than the old newtonian paradigm of causation. Detractors also use the term to signify something empty or meaningless, as they feel it deals with that which is unverifiable. It is often considered the abstract portion of philosophy that deals with insoluble dilemmas such as the idea of first causes, as well as certain irreducible and recurring universal ideas such as being, space, time, knowing, spirit, soul, reality, etc.