The vascular structure in the uterus of most mammals providing oxygen and nutrients for and transferring wastes from the developing fetus WordNet 3.0 & Open English WordNet

The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. Wikipedia

Organ that connects the developing foetus to the uterine wall Wikidata

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

A vascular organ in mammals, except monotremes and marsupials, present only in the female during gestation. It supplies food and oxygen from the mother to the foetus, and passes back waste. It is implanted in the wall of the uterus and links to the foetus through the umbilical cord. It is expelled after birth. Wiktionary