Same word as nonexistent:

absent, airy, baseless, blank, chimerical, dead, defunct, departed, dreamlike, dreamy, empty, ethereal, extinct, extinguished, fancied, few and far between, flimsy, gone, gossamery, groundless, hallucinatory, hypothetical, illusory, imaginary, imagined, immaterial, imponderable, insubstantial, legendary, lost, missing, mythical, negative, null, null and void, passed away, passed on, perished, shadowy, tenuous, ungrounded, unreal, unsubstantial, vacant, vague, vaporous, void, without foundation