If a married person commits adultery, they have sex with someone that they are not married to. She is going to divorce him on the grounds of adultery. sex between someone who is married and someone who is not their wife or husband (avoutrie, from adulterium, from adulter , from adulterare; ADULTERATE). Sexual relations between a married person and someone other than his or her spouse. Prohibitions against adultery are found in virtually every society; Jewish, Christian, and Islamic traditions all condemn it, and in some Islamic countries it is still punishable by death. Attitudes toward adultery in different cultures have varied widely. Under the Code of Hammurabi (18th century BC) in Babylonia it was punishable by death by drowning, and in ancient Rome an offending woman could be killed, though men were not severely punished. In western Europe and North America, adultery by either spouse is a ground for divorce, though in the U.S. the shift to no-fault divorce significantly reduced the importance of adultery as an element in divorce proceedings. The spread of Western ideas of equality in marriage has resulted in pressure for equal marital rights for women in traditional African and Southeast Asian societies
extramarital sex that willfully and maliciously interferes with marriage relations; "adultery is often cited as grounds for divorce
The unfaithfulness of a married person to the marriage bed; sexual intercourse by a married man with another than his wife, or voluntary sexual intercourse by a married woman with another than her husband