Nouns

(n)dullness, obtusenessthe quality of being slow to understand
(n)dullnessthe quality of lacking interestingness“the stories were of a dullness to bring a buffalo to its knees”
(n)dullnessa lack of visual brightness“the brightness of the orange sky was reflected in the dullness of the orange sea”
(n)dullnesslack of sensibility“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.”
(n)dullness, bluntnesswithout sharpness or clearness of edge or point“the dullness of the pencil made his writing illegible”