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
disapproval To fornicate means to have sex with someone you are not married to. + fornication for·ni·ca·tion Fornication is a crime in some American states. a word meaning to have sex with someone who you are not married to - used to show strong disapproval (fornicare, from fornix )