noun (n)

• the consistency of a solid(noun.attribute)

  Synonym:
  solidness
  Antonym:
  porosity, porousness
  

  source: wordnet30
• state of having the interior filled with matter(noun.state)

  Antonym:
  hollowness
  

  source: wordnet30
• the quality of being solid and reliable financially or factually or morally(noun.attribute)

  Example:
  The solidity of the evidence worked in his favor.
  

  source: wordnet30
• The state or quality of being solid; density; consistency, -- opposed to fluidity; compactness; fullness of matter, -- opposed to openness or hollowness; strength; soundness, -- opposed to weakness or instability; the primary quality or affection of matter by which its particles exclude or resist all others; hardness; massiveness.(noun)

  source: webster1913