either of two periods characterized by extreme public fear of Communists and the principles of socialism (during the 1920s and 1950s)
a series of actions by the US government in 1919-20, against people who were believed to be Communists. Many US workers went on strike (=stopped working to protest about their conditions) and the government was worried that there might be a revolution. Because of this, many people were arrested and many foreigners were forced to leave the country