Source : Webster's Revised Unabridged Dictionary (1913)

Existential \Ex`is*ten"tial\, a.
   Having existence. [Archaic] --Bp. Barlow.
   --{Ex`is*ten"tial*ly}, adv. [Archaic]

         Existentially as well as essentially intelligent.
                                                  --Colerige.

Source : WordNet®

existential
     adj 1: derived from experience or the experience of existence; "the
            rich experiential content of the teachings of the
            older philosophers"- Benjamin Farrington; "formal
            logicians are not concerned with existential matters"-
            John Dewey [syn: {experiential}]
     2: of or as conceived by existentialism; "an existential moment
        of choice"
     3: relating to or dealing with existence (especially with human
        existence)