Polygamous rhymes with:
monogamous, anonymous, artemus, autonomous, blasphemous, clackamas, hippopotamus, infamous, magnanimous, monogamous, pusillanimous, synonymous, thalamus, unanimous, venomous
Polygamous sounds like:
pelagians, pelekunu's, pelican's, pelicans, pillaging, placencia, placing, plagens, plaguing, plaisance, plascencia, plasencia, pleasing, plucinski, plucking, plugging, policeman's, policing, polishing, polyconomics, polygynous, publicizing, publishing, publishing's, publishings, pulsing