The Collaborative International Dictionary of English v.0.48:

Decamp \De*camp"\, v. i. [imp. & p. p. Decamped (?; 215); p.
   pr. & vb. n. Decamping.] [F. d['e]camper; pref. d['e]- (L.
   dis) + camp camp. See Camp.]
   1. To break up a camp; to move away from a camping ground,
      usually by night or secretly. --Macaulay.
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   2. Hence, to depart suddenly; to run away; -- generally used
      disparagingly.
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            The fathers were ordered to decamp, and the house
            was once again converted into a tavern. --Goldsmith.
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