A brilliant rebuttal (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
dull
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for dull that I've seen before include "Boring - not sunny" , "Lusterless or uninteresting" , "Lacking excitement" , "mat" , "Monotonous" .)