chorioallantoicPronunciation: /ˌkɔːrɪəʊˌalənˈtəʊɪk, ˌkɒrɪəʊ-/Definition of chorioallantoic adjective Embryology relating to or denoting fused chorionic and allantoic membranes around a fetus. chorioallantoic in other Oxford dictionaries Definition of chorioallantoic in the US English dictionary