n. (pl. placentae or placentas) 1 a flattened circular organ in the uterus of pregnant mammals nourishing and maintaining the foetus through the umbilical cord and expelled after birth. 2 (in flowers) part of the ovary wall carrying the ovules. placental adj.
[ L f. Gk plakous -ountos flat cake f. the root of plax plakos flat plate ]