Mammoth Uncensored Word List:
35 words ending with m, 16 letters long

accommodationism anthropocentrism anthropomorphism antievolutionism antireductionism authoritarianism collaborationism communitarianism configurationism consequentialism controversialism countercriticism counterterrorism electromagnetism electrooculogram electropherogram environmentalism epiphenomenalism gynandromorphism hypercortisolism hyperpituitarism institutionalism internationalism introspectionism mesembryanthemum multiculturalism necessitarianism premillennialism pseudoclassicism psychopannychism spectroheliogram superromanticism supranationalism transnationalism ultranationalism