Function: noun
Etymology: name applied to rebel sympathizers in Madrid in 1936 when four rebel columns were advancing on the city
Date: 1936
: a group of secret sympathizers or supporters of an enemy that engage in espionage or sabotage within defense lines or national borders
– fifth col · um · nism \ - ' kä-l ə m- ˌ (n)i-z ə m \ noun
– fifth col · um · nist \ -(n)ist \ noun