What is the meaning of Dull?

Lacking the ability to cut easily; not sharp.

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

Not bright or intelligent; stupid; having slow understanding.

To render dull; to remove or blunt an edge or something that was sharp.

To soften, moderate or blunt; to make dull, stupid, or sluggish; to stupefy.

To lose a sharp edge; to become dull.

To render dim or obscure; to sully; to tarnish.

Source: wiktionary.org

See also