One man marrying multiple women would be polygyny
One woman marrying multiple men would be polyandry
Polygamy would be a marriage in which three or more people are married to each other or one person is married to two or more people
an example of Poly monogamy that would also be polygyny might be if a man monogamously marries one woman while being monogamously married to a second woman without the two women being married to each otherm. The 2 figuratively became 1 flesh twice