Here's what rhymes with commentarium.
barium aquarium honorarium sanitarium planetarium vivarium Words that almost rhyme with commentarium
carrion nobelium agrarian ovarian barbarian clarion librarian egalitarian sectarian antiquarian chameleon sanitarian vulgarian cnidarian authoritarian libertarian vegetarian communitarian trinitarian parliamentarian nonsectarian centenarian seminarian nonagenarian humanitarian proletarian veterinarian octogenarian utilitarian totalitarian latitudinarian sexagenarian disciplinarian valetudinarian septuagenarian gentium biennium fermium millennium compendium requiem lutetium endometrium proscenium technetium quadrennium lawrencium