noun (n)

• the property of being strong and healthy in constitution(noun.attribute)

  Synonym:
  hardiness, lustiness, validity
  

  source: wordnet30
• the characteristic of being strong enough to withstand intellectual challenge(noun.attribute)

  Example:
  The lack of robustness in the findings may be due to the small size of the sample.
  

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

  source: webster1913