Source : Webster's Revised Unabridged Dictionary (1913)

Incurableness \In*cur"a*ble*ness\, n.
   The state of being incurable; incurability. --Boyle.

Source : WordNet®

incurableness
     n : incapability of being cured or healed [syn: {incurability}]
         [ant: {curability}, {curability}]