noun (n)

• enduring strength and energy(noun.attribute)

  Synonym:
  stamina, staying power
  

  source: wordnet30
• the property of being big and strong(noun.attribute)

  Synonym:
  huskiness, ruggedness
  

  source: wordnet30
• the elasticity and hardness of a metal object; its ability to absorb considerable energy before cracking(noun.attribute)

  Synonym:
  temper
  

  source: wordnet30
• impressive difficulty(noun.attribute)

  Synonym:
  formidability
  

  source: wordnet30
• The quality or state of being tough.(noun)

  source: webster1913