Synonyms for Lifeless (same or very similar meaning)
WordNet sense 1 (holding or containing nothing):
emptyWordNet sense 2 (not animated or enlivened; dull):
unanimatedWordNet sense 3 (not showing characteristics of life especially the capacity to sustain life; no longer exerting force or having energy or heat):
deadWordNet sense 4 (deprived of life; no longer living):
exanimateFrom the ODE community, based on WordNetadd/edit