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.]
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.]
She was uncertain if it were the gypsy or her
wraith. --Sir W.
O, hollow wraith of dying fame. --Tennyson.
2. Sometimes, improperly, a spirit thought to preside over
the waters; -- called also water wraith. --M. G. Lewis.