A woman being married to two men would be an example of:

monogamy

polygyny

polyandry

cohabitation

Polyandry

Explanation:

Polyandry happens when a woman has two or more husbands at the same time. The term stems from Greek poly meaning many and aner meaning men.

This kind of relationship is rather rare and exists mainly in the Himalayan mountains. The purpose of such unions is to provide better for the children as such unions tend to happen in places with limited natural resources, thus making survival difficult.

Societies where polyandry is allowed and accepted are based on hunting and gathering and they usually lead a fairly isolated life.