The Collaborative International Dictionary
Invincible \In*vin"ci*ble\, a. [L. invincibilis: cf. F. invincible. See In- not, and Vincible.] Incapable of being conquered, overcome, or subdued; unconquerable; insuperable; as, an invincible army, or obstacle.
Lead forth to battle these my sons
Invincible.
--Milton.
-- In*vin"ci*ble*ness, n. -- In*vin"ci*bly, adv.
Wiktionary
n. The quality of being invincible; unconquerableness; insuperableness.
Usage examples of "invincibleness".
And in this was portrayed the victory of the spirit over the flesh, the indomitability and moral grandeur of the soul that knows no restriction and rises above time and space and matter with a surety and invincibleness born of nothing else than eternity and immortality.
I know for myself that I was shocked into admiration of the boy, and I saw in him the splendid invincibleness of immortality rising above the flesh and the fears of the flesh, as in the prophets of old, to condemn unrighteousness.