1. That which is without sharpness of an edge or a point: There is a dullness in Alisha's eyes that suggests that she did not get enough sleep last night.
2. A lack of visual brightness: It was so foggy in the afternoon that the dullness got to Debora and she felt that she needed a cup of tea to lift her spirits.
3. That which lacks interest: The speaker’s topic had such a dullness about it that many in the audience got up and left early.
4. A condition or situation that results in being slow to understand or to recognize something: The dullness of the old dog was accentuated by its inability to recognize its owners when they came home.