WordNet sense 1 (having only a limited ability to react chemically; chemically inactive):

indifferent, neutral

WordNet sense 2 (not reacting chemically):

unreactive

WordNet sense 3 (not in motion):

nonmoving

WordNet sense 4 (not active physically or mentally):

inactive

WordNet sense 5 (slow and apathetic):

sluggish, soggy, torpid