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.”

Lacking the ability to cut easily; not sharp.

“All these knives are dull.”

Boring; not exciting or interesting.

“He sat through the dull lecture and barely stayed awake.”

Not shiny; having a matte finish or no particular luster or brightness.

“Choose a dull finish to hide fingerprints.”