The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

         A pathless desert, dusk with horrid shades. --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dusk \Dusk\, n.
   1. Imperfect obscurity; a middle degree between light and
      darkness; twilight; as, the dusk of the evening.
      [1913 Webster]

   2. A darkish color.
      [1913 Webster]

            Whose duck set off the whiteness of the skin.
                                                  --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dusk \Dusk\, v. t.
   To make dusk. [Archaic]
   [1913 Webster]

         After the sun is up, that shadow which dusketh the
         light of the moon must needs be under the earth.
   --Holland.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dusk \Dusk\, v. i.
   To grow dusk. [R.] --Chaucer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dusk
    n 1: the time of day immediately following sunset; "he loved the
         twilight"; "they finished before the fall of night" [syn:
         twilight, dusk, gloaming, gloam, nightfall,
         evenfall, fall, crepuscule, crepuscle]
    v 1: become dusk

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "dusk":
   bad light, blackish, broad day, brown of dusk, brownness,
   caliginous, candlelight, candlelighting, cocklight, crepuscular,
   crepuscule, dark, dark-colored, darken, darkish, darkishness,
   darkle, darksome, darksomeness, dawn, day, day glow, daylight,
   dayshine, daytide, daytime, deadness, dim, dim light, dimmish,
   dimness, dimpsy, drabness, dullness, duskiness, duskingtide,
   duskness, dusky, evening, evensong, eventide, flatness, full sun,
   funereal, gloam, gloaming, gloom, glooming, gloomy, grave,
   green flash, grow dark, grow dim, half-light, lack of sparkle,
   lackluster, lifelessness, light of day, lower, lusterlessness, mat,
   mat finish, midday sun, murk, murkiness, murksome, murky,
   nightfall, nigrescent, noonlight, noontide light, obscure,
   owllight, partial darkness, ray of sunshine, sad, semidark, shine,
   sober, somber, somberness, sombrous, subfusc, sun spark, sunbeam,
   sunbreak, sunburst, sundown, sunlight, sunset, sunsetty, sunshine,
   swart, swarthy, tenebrous, twilight, twilighty, unilluminated,
   vesper, vespertine