noun (n)

• having the strength to withstand attack(noun.state)

  Synonym:
  impregnability
  

  source: wordnet30
• the property of being invulnerable; the property of being incapable of being hurt (physically or emotionally)(noun.attribute)

  Antonym:
  vulnerability
  

  source: wordnet30
• Quality or state of being invulnerable.(noun)

  source: webster1913