The Collaborative International Dictionary of English v.0.48:
Fomenter \Fo*ment"er\, n. One who foments; one who encourages or instigates; as, a fomenter of sedition. [1913 Webster]WordNet (r) 3.0 (2006):
fomenter n 1: one who agitates; a political troublemaker [syn: agitator, fomenter]