Source : Webster's Revised Unabridged Dictionary (1913)

Nonexistent \Non`ex*ist"ent\, a.
   Not having existence.

Source : WordNet®

nonexistent
     adj 1: not having existence or being or actuality; "chimeras are
            nonexistent" [ant: {existent}]
     2: not existing; "innovation has been sadly lacking";
        "character development is missing from the book" [syn: {lacking(p)},
         {missing}, {wanting(a)}]