This denominative verb means to make someone a rival wife—to take a woman as a co-wife to another. Leviticus 18:18 uses it in prohibiting a man from marrying his wife's sister during the wife's lifetime 'to make her a rival.' The Torah recognizes the inherent conflict in such arrangements, forbidding this particular configuration even while polygamy was permitted. The verb's existence reflects the social reality of polygamous marriages and the rivalry dynamics they produced, as seen in Hannah and Peninnah's relationship.