The Collaborative International Dictionary of English v.0.48:

Requisition \Req`ui*si"tion\ (r?k`w?-z?sh"?n), n.[Cf. F.
   r['e]quisition, L. requisitio a searching.]
   1. The act of requiring, as of right; a demand or application
      made as by authority. Specifically:
      (a) (International Law) A formal demand made by one state
          or government upon another for the surrender or
          extradition of a fugitive from justice. --Kent.
      (b) (Law) A notarial demand of a debt. --Wharton.
      (c) (Mil.) A demand by the invader upon the people of an
          invaded country for supplies, as of provision, forage,
          transportation, etc. --Farrow.
      (d) A formal application by one officer to another for
          things needed in the public service; as, a requisition
          for clothing, troops, or money.
          [1913 Webster]

   2. That which is required by authority; especially, a quota
      of supplies or necessaries.
      [1913 Webster]

   3. A written or normal call; an invitation; a summons; as, a
      reqisition for a public meeting. [Eng.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Requisition \Req`ui*si"tion\, v. t.
   1. To make a reqisition on or for; as, to requisition a
      district for forage; to requisition troops.
      [1913 Webster]

   2. To present a requisition to; to summon request; as, to
      requisition a person to be a candidate. [Eng.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

requisition
    n 1: the act of requiring; an authoritative request or demand,
         especially by a military or public authority that takes
         something over (usually temporarily) for military or public
         use
    2: an official form on which a request in made; "first you have
       to fill out the requisition" [syn: requisition,
       requisition form]
    3: seizing property that belongs to someone else and holding it
       until profits pay the demand for which it was seized [syn:
       sequestration, requisition]
    v 1: make a formal request for official services
    2: demand and take for use or service, especially by military or
       public authority for public service [ant: derequisition]