mar·su·pi·um 
(mär-spē-əm)
(mär-spē-əm)n. pl. mar·su·pi·a (-pē-ə)
1. An external pouch or fold on the abdomen of most female marsupials, containing the mammary glands and in which the young continue to develop after leaving the uterus.
2. A temporary pouch in certain fishes, amphibians, and invertebrates in which eggs are carried until hatched. Also called brood pouch.
[Late Latin marsūpium, pouch, from Latin marsīpium, marsuppium, from Greek marsippion, marsuppion, diminutive of marsippos, marsuppos, purse, perhaps of Iranian origin; akin to Avestan marsū-, belly, paunch.]