adultery
n. consensual sexual relations when one of the participants is legally married to another. In some states it is still a crime and and in many states it is grounds for divorce for the spouse of the married adulterer. The criminal charges are almost never brought, and in those states in which there is no-fault divorce (or dissolution), adultery is legally not relevant. Until the 1970s, in community property states adultery was grounds for giving the person cheated upon most of the couple's property, often resulting in lurid and long trials and grist for scandal newspapers.