It is sudden absence of physical effects exerted by the dead object, a singularity, a discontinuity. It is not an inert state of things. Inertia is a balance of forces - and in Death the absence of any force whatsoever is postulated. Death is, therefore, also not an entropic climax. Entropy is an isotropic, homogeneous distribution of energy.
Death is the absence of any and all energies.
While, outwardly, the two might seem identical - they are the two poles of a dichotomy. So, Death, as opposed to inertia or entropy, is not something that modern physics is fully equipped to deal with. Physics, by definition, deals with forces and measurable effects. Actually, this would be a stark contradiction in its terms. Indeed, this definition of Death has reality itself to argue against it.