The Collaborative International Dictionary of English v.0.48:

Motive \Mo"tive\, a.
   Causing motion; having power to move, or tending to move; as,
   a motive argument; motive power. "Motive faculty." --Bp.
   Wilkins.
   [1913 Webster]

   Motive power (Mach.), a natural agent, as water, steam,
      wind, electricity, etc., used to impart motion to
      machinery; a motor; a mover.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Motive \Mo"tive\, n. [F. motif, LL. motivum, from motivus
   moving, fr. L. movere, motum, to move. See Move.]
   1. That which moves; a mover. [Obs.] --Shak.
      [1913 Webster]

   2. That which incites to action; anything prompting or
      exciting to choise, or moving the will; cause; reason;
      inducement; object; motivation[2].
      [1913 Webster]

            By motive, I mean the whole of that which moves,
            excites, or invites the mind to volition, whether
            that be one thing singly, or many things
            conjunctively.                        --J. Edwards.
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   3. (Mus.) The theme or subject; a leading phrase or passage
      which is reproduced and varied through the course of a
      comor a movement; a short figure, or melodic germ, out of
      which a whole movement is develpoed. See also Leading
      motive, under Leading. [Written also motivo.]
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   4. (Fine Arts) That which produces conception, invention, or
      creation in the mind of the artist in undertaking his
      subject; the guiding or controlling idea manifested in a
      work of art, or any part of one.
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   Syn: Incentive; incitement; inducement; reason; spur;
        stimulus; cause.

   Usage: Motive, Inducement, Reason. Motive is the word
          originally used in speaking of that which determines
          the choice. We call it an inducement when it is
          attractive in its nature. We call it a reason when it
          is more immediately addressed to the intellect in the
          form of argument.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Motive \Mo"tive\, v. t.
   To prompt or incite by a motive or motives; to move.
   [1913 Webster]

WordNet (r) 3.0 (2006):

motive
    adj 1: causing or able to cause motion; "a motive force";
           "motive power"; "motor energy" [syn: motive(a),
           motor]
    2: impelling to action; "it may well be that ethical language
       has primarily a motivative function"- Arthur Pap; "motive
       pleas"; "motivating arguments" [syn: motivative(a),
       motive(a), motivating]
    n 1: the psychological feature that arouses an organism to
         action toward a desired goal; the reason for the action;
         that which gives purpose and direction to behavior; "we did
         not understand his motivation"; "he acted with the best of
         motives" [syn: motivation, motive, need]
    2: a theme that is repeated or elaborated in a piece of music
       [syn: motif, motive]
    3: a design or figure that consists of recurring shapes or
       colors, as in architecture or decoration [syn: motif,
       motive]

Moby Thesaurus II by Grady Ward, 1.0:

135 Moby Thesaurus words for "motive":
   activating, active, actuating, aim, ambition, angle, animating,
   animus, antecedent, argument, aspiration, attraction, basis,
   burden, case, causal, causative, cause, chapter, compelling,
   concern, consideration, counsel, desideration, desideratum, design,
   desire, determinant, determination, device, directive, driving,
   effect, emotion, end, enticement, essence, feeling, figure,
   fixed purpose, focus of attention, focus of interest, function,
   gist, goad, goal, grounds, head, heading, idea, impellent,
   impelling, impulsive, in motion, incentive, incitement, inducement,
   inducive, influence, intendment, intent, intention, issue, kinetic,
   leitmotiv, living issue, lure, main point, matter, matter in hand,
   meaning, meat, mind, mobile, motif, motile, motivating,
   motivating force, motivation, motivational, motor, moving, nisus,
   object, objective, operative, passion, pattern, phrase, plan,
   point, point at issue, point in question, pressing, problem, prod,
   project, propellant, propelling, proposal, propulsive, propulsory,
   prospectus, pulsive, purpose, pushing, question, rationale, reason,
   resolution, resolve, rubric, sake, shoving, spring, spur,
   stimulation, stimulus, stirring, striving, study, subject,
   subject matter, subject of thought, substance, text, theme,
   thrusting, topic, transitional, traveling, urge, urgent, view,
   will



Bouvier's Law Dictionary, Revised 6th Ed (1856):

MOTIVE. The inducement, cause or reason why a thing is done.
     2. When there is such a mistake in the motive, that had the truth been
known, the contract would pot have been made, it is generally void., For
example, if a man should, after the death of Titius, of which he was
ignorant, insure his life, the error of the motive would avoid the contract.
Toull. Dr. Civ. Fr. liv. 3, c. 2, art. 1. Or, if Titius should sell to
Livius his horse, which both parties supposed to be living at some distance
from the place where the contract was made, when in fact, the horse was then
dead, the contract would be void. Poth. Vente, n. 4; 2 Kent, Com. 367. When
the contract is entered into under circumstances of clear mistake or
surprise, it will not be enforced. See the following authorities on this
subject. 1 Russ. & M. 527; 1 Ves. jr. 221; 4 Price, 135; 1 Ves. jr. 210;
Atkinson on Titl. 144. Vide Cause; Consideration.
     3. The motive of prosecutions is frequently an object of inquiry,
particularly when the prosecutor is a witness, and in his case, as that of
any other witness, when the motion is ascertained to be bad, as a desire of
revenge for a real or supposed injury, the credibility of the witness will
be much weakened, though this will not alone render him incompetent. See
Evidence; Witness.