Meaning

noun that part of the ovary of a flowering plant where the ovules form

noun the vascular structure in the uterus of most mammals providing oxygen and nutrients for and transferring wastes from the developing fetus

originElision for phrases such as New Latin placenta uterī (“womb cake”), placenta uterina (“uterine cake”), from Latin placenta (“flat cake”), because of the flat round shape of the afterbirth.

Etymology from Wiktionary, CC BY-SA 3.0