noun (n)

• the quality of being slow to understand(noun.cognition)

  Synonym:
  obtuseness
  

  source: wordnet30
• the quality of lacking interestingness(noun.attribute)

  Example:
  The stories were of a dullness to bring a buffalo to its knees.
  

  source: wordnet30
• a lack of visual brightness(noun.attribute)

  Example:
  The brightness of the orange sky was reflected in the dullness of the orange sea.
  

  Antonym:
  brightness
  

  source: wordnet30
• lack of sensibility(noun.attribute)

  Example:
  There was a dullness in his heart.
  Without him the dullness of her life crept into her work no matter how she tried to compartmentalize it..
  

  source: wordnet30
• without sharpness or clearness of edge or point(noun.attribute)

  Example:
  The dullness of the pencil made his writing illegible.
  

  Synonym:
  bluntness
  Antonym:
  keenness, sharpness
  

  source: wordnet30
• The state of being dull; slowness; stupidity; heaviness; drowsiness; bluntness; obtuseness; dimness; want of luster; want of vividness, or of brightness.(noun)

  source: webster1913