CHICAGO PIANO

(slang) a submachine gun. The allusion is to Chicago during the 1920s when it was controlled by gangsters who used machine guns. —PDC Volume 7 Approved Glossary

(slang) a submachine gun. The allusion is to Chicago during the 1920s when it was controlled by gangsters who used machine guns.1. a reference to a submachine gun that first gained underworld acceptance in the Chicago gang wars of the 1920s. The Chicago piano was popular as it was light, easy to operate and could fire up to a thousand shots a minute. The origin of the term is unknown. 2. a World War II (1939-1945) naval nickname for a rapid-firing antiaircraft gun, possibly named after the submachines guns used in the 1920s by American gangsters.