fornication > define

noun

• Voluntary sexual intercourse between persons not married to each other.
• Extramarital sex that willfully and maliciously interferes with marriage relations.
  • usage: "adultery is often cited as grounds for divorce"
  • synonyms: adultery, criminal conversation

• (n.) Idolatry.
• (n.) Unlawful sexual intercourse on the part of an unmarried person; the act of such illicit sexual intercourse between a man and a woman as does not by law amount to adultery.
• (n.) Adultery.
• (n.) Incest.