The Collaborative International Dictionary of English v.0.48:

Commandeer \Com`man*deer"\, v. t. [imp. & p. p. Commandeered;
   p. pr. & vb. n. Commandeering.] [D. kommandeeren to
   command, in South Africa to commandeer, fr. F. commander to
   command. See Command.]
   1. (Mil.) To compel to perform military service; to seize for
      military purposes; -- orig. used of the Boers.
      [Webster 1913 Suppl.]

   2. To take arbitrary or forcible possession of. [Colloq.]
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

commandeer
    v 1: take arbitrarily or by force; "The Cubans commandeered the
         plane and flew it to Miami" [syn: commandeer, hijack,
         highjack, pirate]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "commandeer":
   accroach, annex, appropriate, arrogate, assume, attach, call up,
   collectivize, communalize, communize, confiscate, conscript,
   detach, detach for service, distrain, draft, enlist, enroll,
   expropriate, garnish, impound, impress, induct, join, levy, list,
   mobilize, muster, muster in, nationalize, preempt, press, raise,
   recruit, replevin, replevy, seize, sequester, sequestrate, sign on,
   sign up, socialize, summon, take, usurp