Main Entry: al·lan·to·is

Pronunciation: \ə-ˈlan-tə-wəs\

Function: noun

Inflected Form(s): plural al·lan·to·ides \ˌa-lən-ˈtō-ə-ˌdēz, ˌa-ˌlan-\

Etymology: New Latin, ultimately from Greek allant-, allas sausage

Date: 1646

: a vascular fetal membrane of reptiles, birds, and mammals that is formed as a pouch from the hindgut and that in placental mammals is intimately associated with the chorion in formation of the placenta

— al·lan·to·ic \ˌa-lən-ˈtō-ik, ˌa-ˌlan-\ adjective