C.I.O.

1. chief investment officer.

2. See Congress of Industrial Organizations.

Also, CIO.

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CIO (no periods) or C.I.O.,

Congress of Industrial Organizations, a group of labor unions organized on a permanent basis in 1938. It merged with the AFL in 1955. The unions in the CIO are organized according to industries (such as the auto workers and the electrical workers); in the AFL they are organized according to crafts (such as the carpenters and the machinists).