Source : Webster's Revised Unabridged Dictionary (1913)

Invulnerability \In*vul"ner*a*bil`i*ty\, n. [Cf. F.
   invuln['e]rabilit['e].]
   Quality or state of being invulnerable.

Source : WordNet®

invulnerability
     n 1: having the strength to withstand attack [syn: {impregnability}]
     2: the property of being invulnerable; the property of being
        incapable of being hurt (physically or emotionally) [ant:
        {vulnerability}]