ghost

Concise Oxford English Dictionary © 2008 Oxford University Press:
ghost/ɡəʊst/

▶noun

• 1 an apparition of a dead person which is believed to appear to the living, typically as a nebulous image.

  ■ archaic a spirit or soul.

• 2 a faint trace: the ghost of a smile.

• 3 a faint secondary image produced by a fault in an optical system or on a cathode ray screen.

▶verb

• 1 act as ghostwriter of.

• 2 glide smoothly and effortlessly.

– phrases
the ghost in the machine Philosophy the mind viewed as distinct from the body.
give up the ghost die or stop functioning.

– derivatives
ghostlike adjective.

– origin OE gāst, of Gmc origin.