Definition of blue light in US English:

blue light


  • 1Nautical. A pyrotechnic preparation which burns with a blue flame and is used to send signals, especially at night-time. Now historical.

  • 2US informal (chiefly derogatory). A New England federalist who opposed the Anglo-American war of 1812–15; (later more generally) a federalist, a person perceived as disloyal. Frequently attributive Now historical.


Mid 18th century; earliest use found in Richard Cambridge (1717–1802), poet and essayist. From blue + light.


blue light

/ˌbluː ˈlʌɪt/