Definition of fifth columnist in US English:

fifth columnist

noun

  • See fifth column

    • ‘One of the main themes is the threat posed by fifth columnists, and Fred, despite his admirable single-mindedness, is dangerously naïve in his dealings with strangers.’
    • ‘The film contains an imaginary radio broadcast in which listeners are alerted to be on the lookout for fifth columnists.’
    • ‘Does Ms. West not think such fifth columnists exist?’
    • ‘Insurrectionists, traitors and fifth columnists were a feature of our political landscape.’
    • ‘Some opposition politicians and businessmen are also taking on the role of the fifth columnists.’

Pronunciation

fifth columnist

/ˌfɪ(f)θ ˈkɑləmnəst//ˌfi(f)TH ˈkäləmnəst/