Secession
WordNet
noun
(1) Formal separation from an alliance or federation
(2) The withdrawal of eleven southern states from the Union in 1860 which precipitated the American Civil War
(3) An Austrian school of art and architecture parallel to the French art nouveau in the 1890s
WiktionaryText
Usage notes
A common example of usage is the withdrawal of 11 Southern states of the United States of America from the Union in 1860–1861, precipitating the U.S. civil war