The Collaborative International Dictionary of English v.0.48:

Motivate \Mo"ti*vate\, v. t. [imp. & p. p. -vated; p. pr. &
   vb. n. -vating.] [From Motive, n.]
   To provide with a motive; to move; impel; induce; incite. --
   Mo`ti*va"tion, n. --William James.

   Syn: move, prompt, incite, induce impel, drive.
        [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

motivate
    v 1: give an incentive for action; "This moved me to sacrifice
         my career" [syn: motivate, actuate, propel, move,
         prompt, incite]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "motivate":
   activate, actuate, animate, arouse, bring, bring about, bring on,
   cajole, call forth, cause, coax, compel, contrive, draw down,
   draw on, drive, drive on, effect, egg on, elicit, encourage,
   energize, evoke, excite, force, forward, foster, galvanize, get,
   give an impetus, give momentum, goad, impel, incite, induce,
   influence, inspire, instigate, lead, mobilize, move,
   move to action, nudge, obtain, occasion, persuade, pique, power,
   procure, prod, promote, prompt, propel, provoke, push,
   put in motion, quicken, rouse, set agoing, set going,
   set in motion, shove, spark, spur, stimulate, stir up, superinduce,
   tempt, thrust, urge, wheedle, whip on