Found 2 items, similar to allantois.
English → English (WordNet) Definition: allantois allantois n : vascular fetal membrane that develops from the hindgut in embryonic higher vertebrates (reptiles, birds and mammals)
English → English (gcide) Definition: Allantois Allantois \Al*lan"to*is\, Allantoid \Al*lan"toid\, ] n.. (Anat.) A membranous appendage of the embryos of mammals, birds, and reptiles, -- in mammals serving to connect the fetus with the parent; the urinary vesicle. [1913 Webster]