The Collaborative International Dictionary of English v.0.48:
Dullness \Dull"ness\, n. The state of being dull; slowness; stupidity; heaviness; drowsiness; bluntness; obtuseness; dimness; want of luster; want of vividness, or of brightness. [Written also dulness.] [1913 Webster] And gentle dullness ever loves a joke. --Pope. [1913 Webster]