The Collaborative International Dictionary of English v.0.48:

Wraith \Wraith\, n. [Scot. wraith, warth; probably originally, a
   guardian angel, from Icel. v["o]r[eth]r a warden, guardian,
   akin to E. ward. See Ward a guard.]
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   1. An apparition of a person in his exact likeness, seen
      before death, or a little after; hence, an apparition; a
      specter; a vision; an unreal image. [Scot.]
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            She was uncertain if it were the gypsy or her
            wraith.                               --Sir W.
                                                  Scott.
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            O, hollow wraith of dying fame.       --Tennyson.
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   2. Sometimes, improperly, a spirit thought to preside over
      the waters; -- called also water wraith. --M. G. Lewis.
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