Source : Webster's Revised Unabridged Dictionary (1913)

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

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

Source : WordNet®

motive power
     n : the power or ability to move [syn: {locomotion}, {motivity}]