Definition of bug light in US English:

bug light

noun

North American
  • 1Nautical a light positioned at sea or on land, or displayed by a vessel, which serves as a beacon, warning, alert, or guide for ships.

  • 2A lantern or torch; = sense 14 (now rare).

  • 3An electric light bulb giving a yellow glow, used in outdoor lighting, as being less attractive to flying insects than a standard bulb.

Origin

Mid 19th century.