Ghost definition from Dictionary.com

[Chronos]

Dictionary.com Unabridged (v 1.1)

–noun

1. the soul of a dead person, a disembodied spirit imagined, usually as a vague, shadowy or evanescent form, as wandering among or haunting living persons. 
2. a mere shadow or semblance; a trace: He's a ghost of his former self. 
3. a remote possibility: He hasn't a ghost of a chance. 
4. (sometimes initial capital letter) a spiritual being. 
5. the principle of life; soul; spirit. 
6. Informal. ghost writer. 
7. a secondary image, esp. one appearing on a television screen as a white shadow, caused by poor or double reception or by a defect in the receiver. 
8. Also called ghost image. Photography. a faint secondary or out-of-focus image in a photographic print or negative resulting from reflections within the camera lens. 
9. an oral word game in which each player in rotation adds a letter to those supplied by preceding players, the object being to avoid ending a word. 
10. Optics. a series of false spectral lines produced by a diffraction grating with unevenly spaced lines. 
11. Metalworking. a streak appearing on a freshly machined piece of steel containing impurities. 
12. a red blood cell having no hemoglobin. 
13. a fictitious employee, business, etc., fabricated esp. for the purpose of manipulating funds or avoiding taxes: Investigation showed a payroll full of ghosts. 

–verb (used with object)

14. to ghostwrite (a book, speech, etc.). 
15. to haunt. 
16. Engraving. to lighten the background of (a photograph) before engraving. 

–verb (used without object)

17. to ghostwrite. 
18. to go about or move like a ghost. 
19. (of a sailing vessel) to move when there is no perceptible wind. 
20. to pay people for work not performed, esp. as a way of manipulating funds. 

–adjective

21. fabricated for purposes of deception or fraud: We were making contributions to a ghost company.