Source : Webster's Revised Unabridged Dictionary (1913)

Preexistent \Pre`["e]x*ist"ent\, a.
   Existing previously; preceding existence; as, a
   pre["e]xistent state. --Pope.

Source : WordNet®

preexistent
     adj : existing previously or before something; "variations on
           pre-existent musical themes" [syn: {pre-existent}, {preexisting},
            {pre-existing}]