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.
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   2. To overtake with night or darkness, especially before the
      end of a day's journey or task.
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            Some virgin, sure, . . . benighted in these woods.
                                                  --Milton.
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   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):

benight
    v 1: overtake with darkness or night
    2: envelop with social, intellectual, or moral darkness; "The
       benighted peoples of this area"
    3: make darker and difficult to perceive by sight [syn:
       benight, bedim]