de·cid·u·ate \ ̷ ̷ˈ ̷ ̷ ̷ ̷_wə̇t\adjective Etymology: New Latin deciduatus, from decidua + Latin -atus -ate 1.of a placenta: having the fetal and maternal tissues firmly interlocked so that a layer of maternal tissue is torn away at parturition and forms a part of the afterbirth 2.: deciduous