To render dull; to remove or blunt an edge or something that was sharp.
Years of misuse have dulled the tools.
To soften, moderate or blunt; to make dull, stupid, or sluggish; to stupefy.
He drinks to dull the pain.
To lose a sharp edge; to become dull.
A razor will dull with use.
To render dim or obscure; to sully; to tarnish.