The Collaborative International Dictionary of English v.0.48:

Secession \Se*ces"sion\ (s[-e]*s[e^]sh"[u^]n), 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.
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   2. (U.S. Hist.) The withdrawal of a State from the national
      Union.
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   Secession Church (in Scotland). See Seceder.
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