Definitions for "Ghost Light"
A light left on when the theatre is locked up for the night.
A common theatre practice of leaving a single bare-bulb lamp burning in the middle of the stage all night. In theatre lore, most venues are believed to be haunted; therefore the “Ghost Light” is left on overnight so that the ghosts can see in the dark.
An unexplainable light visible to the naked eye.  It may be seen traveling in a conscious manner, giving the appearance of intelligence.