The Collaborative International Dictionary of English v.0.48:

benight \be*night"\ (b[-e]*n[imac]t"), v. t. [imp. & p. p.
   Benighted; p. pr. & vb. n. Benighting.]
   1. To involve in darkness; to shroud with the shades of
      night; to obscure. [Archaic]
      [1913 Webster]

            The clouds benight the sky.           --Garth.
      [1913 Webster]

   2. To overtake with night or darkness, especially before the
      end of a day's journey or task.
      [1913 Webster]

            Some virgin, sure, . . . benighted in these woods.
                                                  --Milton.
      [1913 Webster]

   3. To involve in moral darkness, or ignorance; to debar from
      intellectual light.
      [1913 Webster]

            Shall we to men benighted
            The lamp of life deny ?               --Heber.
      [1913 Webster]

WordNet (r) 3.0 (2006):

benighted
    adj 1: overtaken by night or darkness; "benighted (or nighted)
           travelers hurrying toward home" [syn: benighted,
           nighted]
    2: lacking enlightenment or knowledge or culture; "this
       benighted country"; "benighted ages of barbarism and
       superstition"; "the dark ages"; "a dark age in the history of
       education" [syn: benighted, dark]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "benighted":
   ableptical, amaurotic, backward, bereft of light, blind,
   color-blind, dark, dim-sighted, empty-headed, eyeless, hemeralopic,
   ignorant, illiterate, in darkness, in the dark, know-nothing,
   mind-blind, naive, night-overtaken, nyctalopic, rayless, sightless,
   spiritually blind, stark blind, stone-blind, undiscerning,
   uneducated, unenlightened, uninformed, uninstructed, unlettered,
   unobserving, unperceiving, unprogressive, unschooled, unseeing,
   untaught, untutored, visionless