The Collaborative International Dictionary of English v.0.48:

Evacuation \E*vac`u*a"tion\, n. [L. evacuatio: cf. F.
   ['e]vacuation.]
   1. The act of emptying, clearing of the contents, or
      discharging. Specifically:
      (a) (Mil.) Withdrawal of troops from a town, fortress,
          etc.
      (b) (Med.) Voidance of any matter by the natural passages
          of the body or by an artificial opening; defecation;
          also, a diminution of the fluids of an animal body by
          cathartics, venesection, or other means.
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   2. That which is evacuated or discharged; especially, a
      discharge by stool or other natural means. --Quincy.
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   3. Abolition; nullification. [Obs.] --Hooker.
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   Evacuation day, the anniversary of the day on which the
      British army evacuated the city of New York, November 25,
      1783.
      [1913 Webster]