a. 1. Of or pertaining to the placenta; having, or characterized by having, a placenta; as, a placental mammal. [ 1913 Webster ]
2. (Zool.) Of or pertaining to the Placentalia. [ 1913 Webster ]
n. (Zool.) One of the Placentalia. [ 1913 Webster ]
‖n. pl. [ NL. ] (Zool.) A division of Mammalia including those that have a placenta, or all the orders above the marsupials. [ 1913 Webster ]