What is the meaning of dullness?

noun

• The quality of being slow to understand.
  • synonyms: obtuseness
• The quality of lacking interestingness.
  • usage: "the stories were of a dullness to bring a buffalo to its knees"
• A lack of visual brightness.
  • usage: "the brightness of the orange sky was reflected in the dullness of the orange sea"
• Lack of sensibility.
  • usage: "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."
• Without sharpness or clearness of edge or point.
  • usage: "the dullness of the pencil made his writing illegible"
  • synonyms: bluntness