Source : Webster's Revised Unabridged Dictionary (1913)

Dusk \Dusk\, a. [OE. dusc, dosc, deosc; cf. dial. Sw. duska to
   drizzle, dusk a slight shower. ???.]
   Tending to darkness or blackness; moderately dark or black;
   dusky.

         A pathless desert, dusk with horrid shades. --Milton.

Dusk \Dusk\, n.
   1. Imperfect obscurity; a middle degree between light and
      darkness; twilight; as, the dusk of the evening.

   2. A darkish color.

            Whose duck set off the whiteness of the skin.
                                                  --Dryden.

Dusk \Dusk\, v. t.
   To make dusk. [Archaic]

         After the sun is up, that shadow which dusketh the
         light of the moon must needs be under the earth.
   --Holland.

Dusk \Dusk\, v. i.
   To grow dusk. [R.] --Chaucer.

Source : WordNet®

dusk
     n : the time of day immediately following sunset; "he loved the
         twilight"; "they finished before the fall of night" [syn:
          {twilight}, {gloaming}, {nightfall}, {evenfall}, {fall},
          {crepuscule}, {crepuscle}]