noun (n)

• an oppressive quality that is laborious and solemn and lacks grace or fluency(noun.attribute)

  Example:
  A book so serious that it sometimes subsided into ponderousness.
  

  Synonym:
  heaviness
  

  source: wordnet30
• the property of being large in mass(noun.attribute)

  Synonym:
  heft, heftiness, massiveness, ponderosity
  

  source: wordnet30
• The quality or state of being ponderous; ponderosity.(noun)

  source: webster1913