wraith

n. spirit of one dead, ghost, specter, ghost of a dead person; ghostly image of someone; apparition of a living person that predicts the person's imminent death, exact resemblance of a living person just before death ; faint trace; something that is pale or weak and has no clear shape; gaseous or vaporous column that is hardly visible

The word "wraith" is first attested in 1513, with the meaning of "ghost or spectre" (that is, an apparition of a living or once-living being, possibly as a portent of death). In 18th century Scotland it was applied to aquatic spirits. Over time, it came to be used in a metaphoric sense to refer to wraith-like things, and to portents in general.
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Noun
1. a mental representation of some haunting experience; "he looked like he had seen a ghost"; "it aroused specters from his past"
(synonym) ghost, shade, spook, specter, spectre
(hypernym) apparition, phantom, phantasm, phantasma, shadow

(n.)
Sometimes, improperly, a spirit thought to preside over the waters; -- called also water wraith.
  

(n.)
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.
  

Wraith, Wraie The fleeting apparition of a person, about the moment of death, to another person in kinship or psychomagnetic sympathy. Though wraith may cover different cases, in general it is due to the mayavi-rupa of the person who is dying. It is produced by his thought, though he is unaware of the effect he is producing. An intense and anxious thought about the person he wishes to see becomes objective to the seer, and the apparition wears the aspect and commonly the ordinary clothing of the dying person. In some cases the apparition may not be due to any thought on the part of the dying person, but to abnormal sensitiveness or clairvoyance on the part of the seer. Being in close sympathy with the dying one, he bears the image of that one in his latent memory; and when the event occurs, his higher senses, being aware of it, cause the objectivization of this memory as a visual apparition. The thought itself is objective to a mind capable of perception on that plane; but to become objective to the physical senses, it must clothe itself in matter of a lower grade; and this objectivization may vary from a picture in the mind's eye to an apparition seen by the physical vision. In any case the organism of the seer can provide the necessary vehicle for such an objectivization. Distance plays no part in the phenomenon, and there is no projection of a physically substantial body through space from one place to another. The above case should be distinguished from an appearance of the astral double seen near the graves of the recently deceased. See also EIDOLON; PHANTOM; SPECTER