Dull

adjective

1. tedious, uninteresting
2. lacking zest (see zest sense 2) or vivacity : listless
3. slow in action : sluggish
4. lacking sharpness of edge or point
5. not resonant or ringing
6. lacking in force, intensity, or sharpness
7. lacking brilliance or luster
8. cloudy
9. low in saturation (see saturation sense 4a) and low in lightnessof a color
10. mentally slow : stupid
11. slow in perception or sensibility : insensible