fornication
n. sexual intercourse between a man and woman who are not married to each other. This usage comes from Latin fornicari, meaning vaulted, which became the nickname for brothel, because prostitutes operated in a vaulted underground cavern in Rome. Fornication is still a misdemeanor in some states, as is adultery (sexual intercourse by a married person with someone not his/her spouse), but is virtually never prosecuted. If such anachronistic laws were enforced, the jails of America would have no room for robbers, murderers and drug dealers.