1. [n]  a mental representation of some haunting experience; "he looked like he had seen a ghost"; "it aroused specters from his past"
2. [n]  a suggestion of some quality; "there was a touch of sarcasm in his tone"; "he detected a ghost of a smile on her face"
3. [n]  the visible disembodied soul of a dead person
4. [n]  a writer who gives the credit of authorship to someone else
5. [v]  write for someone else; "How many books have you ghostwritten so far?"
6. [v]  haunt like a ghost; pursue; "Fear of illness haunts her"
7. [v]  move like a ghost; "The masked men ghosted across the moonlit yard"

Ghost
The author of Prism of the Night takes readers into the world of real-life ghost hunters, revealing their high- and low-tech methods for rooting out spirits. Reprint.

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1. \Ghost\, n. [OE. gast, gost, soul, spirit, AS. g[=a]st
   breath, spirit, soul; akin to OS. g?st spirit, soul, D.
   geest, G. geist, and prob. to E. gaze, ghastly.]
   1. The spirit; the soul of man. [Obs.]
            Then gives her grieved ghost thus to lament.
                                                  --Spenser.
   2. The disembodied soul; the soul or spirit of a deceased
      person; a spirit appearing after death; an apparition; a
      specter.
            The mighty ghosts of our great Harrys rose. --Shak.
            I thought that I had died in sleep, And was a
            blessed ghost.                        --Coleridge.
   3. Any faint shadowy semblance; an unsubstantial image; a
      phantom; a glimmering; as, not a ghost of a chance; the
      ghost of an idea.
            Each separate dying ember wrought its ghost upon the
            floor.                                --Poe.
   4. A false image formed in a telescope by reflection from the
      surfaces of one or more lenses.
   {Ghost moth} (Zo["o]l.), a large European moth {(Hepialus
      humuli)}; so called from the white color of the male, and
      the peculiar hovering flight; -- called also {great
      swift}.
   {Holy Ghost}, the Holy Spirit; the Paraclete; the Comforter;
      (Theol.) the third person in the Trinity.
   {To} {give up or yield up} {the ghost}, to die; to expire.
            And he gave up the ghost full softly. --Chaucer.
            Jacob . . . yielded up the ghost, and was gathered
            unto his people.                      --Gen. xlix.
                                                  33.
   

2. \Ghost\, v. i.
   To die; to expire. [Obs.] --Sir P. Sidney.
   

3. \Ghost\, v. t.
   To appear to or haunt in the form of an apparition. [Obs.]
   --Shak.
   

(Or "zombie") The image of a user's session on IRC and similar systems, left when the session has been terminated (properly or, often, improperly) but the server (or the network at large) believes the connection is still active and belongs to a real user.

Compare clonebot.

an old Saxon word equivalent to soul or spirit. It is the translation of the Hebrew _nephesh_ and the Greek _pneuma_, both meaning "breath," "life," "spirit," the "living principle" (Job 11:20; Jer. 15:9; Matt. 27:50; John 19:30). The expression "to give up the ghost" means to die (Lam. 1:19; Gen. 25:17; 35:29; 49:33; Job 3:11). (See HOLY GHOST.)