incest: sexual contact customarily or legally forbidden on the criterion of the close kinship of the two people, variably defined on the basis of genealogical or totemic descent, or by reason of marriage or adoption [from Latin,
incestus, unchaste]. Sexual intercourse between persons to whom it is locally forbidden by law or custom because of their relatedness as kinsfolk to totemic clanfolk. The degree of relatedness varies among societies, and the relationship need not be genealogical.
Dictionary of Sexology Project: Main Index