THESAURUS
gadfly
abettor, actuator, animator, cajoler, coax, coaxer, encourager, energizer, firer, gad, galvanizer, goad, impeller, inducer, inspirer, lash, mover, moving spirit, oxgoad, persuader, pleader, prick, prime mover, prod, prompter, rowel, spark, spark plug, sparker, spur, stimulator, sting, tempter, wheedler, whip, whiplash