From The Collaborative International Dictionary of English v.0.48 :
Nonexistence \Non`ex*ist"ence\, n. 1. The state of not existing; absence of existence; the negation of being; -- usually used with reference to existince in the real world, or logical possiblity; as, the nonexistence of vaporware does not go unnoticed long. --A. Baxter. Syn: nonentity[1]. [1913 Webster +PJC] 2. A thing that has no existence. --Sir T. Browne. [1913 Webster]From WordNet (r) 3.0 (2006) :
nonexistence n 1: the state of not existing [syn: nonexistence, nonentity] [ant: being, beingness, existence]