n the quality of lacking interestingness
the stories were of a dullness to bring a buffalo to its knees
n a lack of visual brightness
the brightness of the orange sky was reflected in the dullness of the orange sea
n lack 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 without sharpness or clearness of edge or point
the dullness of the pencil made his writing illegible