sixth column

English

Etymology

Extension of fifth column.

Noun

sixth column (plural sixth columns)

1. An additional group, beyond an identified fifth column, of people which clandestinely undermines a larger group, such as a nation, to which it is expected to be loyal.
   • 1940 June 3, The Sun News-Pictorial, Melbourne, page 3, column 3:

     If the Government is talking about suppressing a Fifth Column, why raise a Sixth Column?

   • 1940 September 20, The Advertiser, Adelaide, page 24, column 4:

     True, we have people of the fifth column, and, unfortunately, the sixth column, with us; they have them in every country; but so far in this war the British diplomatic and secret service has not been so successful as that clever, astute brute-man Hitler and his agents.

2. Used other than figuratively or idiomatically: see sixth,‎ column.