As a noun secession
is secession.
As a verb disaffiliate is
to cease to have an affiliation with; to take steps to break an affiliation or association.
secession
English
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
Related terms
* secessionist
disaffiliate
English
Verb
(disaffiliat)
To cease to have an affiliation with; to take steps to break an affiliation or association.