Source : Webster's Revised Unabridged Dictionary (1913)

Disillusionment \Dis`il*lu"sion*ment\, n.
   The act of freeing from an illusion, or the state of being
   freed therefrom.

Source : WordNet®

disillusionment
     n : freeing from false belief or illusions [syn: {disenchantment},
          {disillusion}]