secession

The act of seceding.

The withdrawal of 11 Southern states from the Union in 1860–1861, precipitating the US Civil War.

The act of seceding or withdrawing; withdrawal; retirement; seclusion; detachment; separation.

Specifically, the act of seceding or withdrawing from a religious or political organization or association; formal withdrawal.

In Scottish eccles. hist., the separation from the Established Church of Scotland which originated in 1733; hence, the whole body of the members of the Secession Church (which see, below).