Secession \Se*ces"sion\, n. [L. secessio: cf. F. s['e]cession. See {Secede}.] 1. The act of seceding; separation from fellowship or association with others, as in a religious or political organization; withdrawal. 2. (U.S. Hist.) The withdrawal of a State from the national Union. {Secession Church} (in Scotland). See {Seceder}.