agitator, agitprop, capper, catalyst, come-on man, decoy, demagogue, exciter, firebrand, fomenter, incendiary, inciter, inflamer, instigator, mischief-maker, plant, provocateur, provoker, rabble-rouser, ringleader, rouser, seditionary, seditionist, shill, stool pigeon, stoolie, troublemaker, urger