The Collaborative International Dictionary of English v.0.48:
Incurableness \In*cur"a*ble*ness\, n. The state of being incurable; incurability. --Boyle. [1913 Webster]WordNet (r) 3.0 (2006):
incurableness n 1: incapability of being cured or healed [syn: incurability, incurableness] [ant: curability, curableness]