The Collaborative International Dictionary of English v.0.48:

Sightless \Sight"less\, a.
   1. Lacking sight; without sight; blind.
      [1913 Webster]

            Of all who blindly creep or sightless soar. --Pope.
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   2. That can not be seen; invisible. [Obs.]
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            The sightless couriers of the air.    --Shak.
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   3. Offensive or unpleasing to the eye; unsightly; as,
      sightless stains. [R.] --Shak.
      [1913 Webster] -- Sight"less*ly, adv.-
      Sight"less*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sightlessness
    n 1: the state of being blind or lacking sight [syn:
         blindness, sightlessness, cecity]