Incest

Chamber's Twientieth Century Dictionary · 1908 · p. 53

in′sest, n. sexual intercourse within the prohibited degrees of kindred.— adj. Incest′ūous , guilty of incest.— adv. Incest′uously .— n. Incest′uousne . [Fr.,—L. incest us — in , not, cast us , chaste.]