Definition of foo fighter in English:

foo fighter

noun

  • An unidentified flying object of a kind reported by US pilots during World War II, usually described as a bright light or ball of fire.

    • ‘The above is a typical example of an encounter with a ‘foo fighter.’’
    • ‘Some RCAF buddies talk about the foo fighters they saw over Europe in the last real war.’

Origin

1940s: from the comic strip Smokey Stover (created in 1935 by Bill Holman (1903–1987)), whose title character used the invented term to mean firefighter.

Pronunciation:

foo fighter

/ˈfo͞o ˌfīdər/