Definition of foo fighter in English:

foo fighter

noun

  • An unidentified flying object, originally one of a kind reported by US pilots during the Second World War, 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 ‘Where there's foo there's fire’, a nonsense catchphrase from the US Smoky Stover cartoon strip.

Pronunciation

foo fighter

/ˈfuː ˌfʌɪtə/