Millionth rhymes with:
billionth, billionth, billionth, billionth, corinth, eleventh, eranthe, seventh, threemonth, absinthe, amaranth, billionth, coelacanth, corinth, cynth, drenth, dushyanth, eighteenth, eleventh, eranthe, fifteenth, fourteenth, helminth, hyacinth, hyacinthe, jacinth, jacinthe, labyrinth, month, nineteenth, ninth, nth, plinth, rhodanthe, seventeenth, seventh, sixteenth, tenth, thirteenth, threemonth, umpteenth
Millionth sounds like:
mainland, malamud, malamute, maland, malinda, malinde, mayland, melamed, meland, melantha, melendy, melinda, melland, milholland, moland, molenda, mulholland