[mar.su.pi.um] n, pl -pia [NL, fr. L, purse, pouch, fr. Gk marsypion] (1698) 1: an abdominal pouch that is formed of a fold of the skin and encloses the mammary glands of most marsupials
2: any of several structures in various invertebrates (as a bryozoan or mollusk) for enclosing or carrying eggs or young