Congress of Industrial Organizations in British English
noun
(in the US) a federation of industrial unions formed in 1935. It united with the AFL in 1955 to form the AFL-CIO
Abbreviation: CIO
Congress of Industrial Organizations in American English
US
a group of affiliated labor unions in the U.S. and Canada, founded in 1938 and merged with the American Federation of Labor in 1955 to form the AFL-CIO