The Collaborative International Dictionary of English v.0.48:

Manipulate \Ma*nip"u*late\, v. i.
   To use the hands in dexterous operations; to do hand work;
   specifically, to manage the apparatus or instruments used in
   scientific work, or in artistic or mechanical processes;
   also, specifically, to use the hand in mesmeric operations.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Manipulate \Ma*nip"u*late\, v. t. [imp. & p. p. Manipulated;
   p. pr. & vb. n. Manipulating.] [LL. manipulatus, p. p. of
   manipulare to lead by the hand, fr. L. manipulus. See
   Maniple.]
   1. To treat, work, or operate with the hands, especially when
      knowledge and dexterity are required; to manage in hand
      work; to handle; as, to manipulate scientific apparatus.
      [1913 Webster]

   2. To control the action of, by management; as, to manipulate
      a convention of delegates; also, to manage artfully or
      fraudulently; as, to manipulate accounts, or election
      returns; to manipulate the stock market.
      [1913 Webster]

WordNet (r) 3.0 (2006):

manipulate
    v 1: influence or control shrewdly or deviously; "He manipulated
         public opinion in his favor" [syn: manipulate, pull
         strings, pull wires]
    2: hold something in one's hands and move it
    3: tamper, with the purpose of deception; "Fudge the figures";
       "cook the books"; "falsify the data" [syn: fudge,
       manipulate, fake, falsify, cook, wangle,
       misrepresent]
    4: manipulate in a fraudulent manner; "rig prices" [syn: rig,
       manipulate]
    5: control (others or oneself) or influence skillfully, usually
       to one's advantage; "She manipulates her boss"; "She is a
       very controlling mother and doesn't let her children grow
       up"; "The teacher knew how to keep the class in line"; "she
       keeps in line" [syn: manipulate, keep in line, control]
    6: treat manually, as with massage, for therapeutic purposed