Source : Webster's Revised Unabridged Dictionary (1913)

Dull \Dull\, v. t. [imp. & p. p. {Duller}; p. pr. & vb. n.
   {Dulling}.]
   1. To deprive of sharpness of edge or point. ``This . . .
      dulled their swords.'' --Bacon.

            Borrowing dulls the edge of husbandry. --Shak.

   2. To make dull, stupid, or sluggish; to stupefy, as the
      senses, the feelings, the perceptions, and the like.

            Those [drugs] she has Will stupefy and dull the
            sense a while.                        --Shak.

            Use and custom have so dulled our eyes. --Trench.

   3. To render dim or obscure; to sully; to tarnish. ``Dulls
      the mirror.'' --Bacon.

   4. To deprive of liveliness or activity; to render heavy; to
      make inert; to depress; to weary; to sadden.

            Attention of mind . . . wasted or dulled through
            continuance.                          --Hooker.