A clandestine subversive organization working within a country to further an invading enemy's military and political aims.
A group of people who aid the enemy from within their own country.
Other Word Forms
Origin of fifth-column
- First applied in 1936 to rebel sympathizers inside Madrid when four columns of rebel troops were attacking that city
From American Heritage Dictionary of the English Language, 5th Edition
- 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 quinta columna consisting of his militant supporters within the capital, intent on undermining the Republican government from within.