Defense of Marriage Act (DOMA)

Definition from Nolo’s Plain-English Law Dictionary

So-called Defense of Marriage laws define marriage as a relationship between one man and one woman, for the purpose of excluding same-sex couples from the institution of marriage. The federal DOMA prohibits the federal government from recognizing same-sex legal relationships entered into in one of the states that recognize same-sex unions. Individual states' DOMA laws provide that those states do not allow same-sex marriage and, often, do not recognize same-sex unions from other states.

Definition provided by Nolo’s Plain-English Law Dictionary.