fifth column
noun
Forms fifth columns 5th column
- noun A group of people which clandestinely undermines a larger group, such as a nation, to which it is expected to be loyal.
- noun Used other than figuratively or idiomatically: see fifth, column.
Synonyms
Etymology
From a 1936 radio address by Spanish Nationalist general Emilio Mola, in which he spoke of four of his army columns moving on Madrid and a fifth column (quinta columna) consisting of his militant supporters within the capital, intent on undermining the Republican government from within.
Sources: Wiktionary · WordNet 3.0 — from the Wiktionary entry “fifth column”, CC BY-SA 4.0. Details