Definitions

1. adjective

relating to or derived from the allantois, a membrane in an embryo that develops into part of the urinary and reproductive systems

“The allantoic cavity in the chick embryo is crucial for gas exchange and waste removal.”

2. noun

the allantois, especially in the early stages of development

“The allantoic sac in the mammalian embryo is a temporary structure that eventually disappears.”