Simple past tense and past participle of dull. (verb)
Examples of word dulled
A pained expression dulled his features, and he shook his head.
On the battlements above, Jonat - helmet gone, sword dulled - watched helplessly as the Vagrians swept over the ramparts.
He has documented his experimental research which has demonstrated that the "executive function" of the brain – the part that controls thinking, problem solving and task completion – has been significantly affected, and 'dulled' – by exposure to electronic media.
I have had some people tell me that he was drinking on the red carpet. so maybe he had kind of dulled his senses.
One that has been, for whatever reason, "dulled" by some purely physical phenomenon.