allantoid /əˈlæntɔɪd/adjective 2noun 1forms 3 adjective2 •Sausage-shaped; especially with reference to fungal spores that are long with rounded ends. •Allantoic. noun1 •(no longer used) The allantois.The allantoide in some animals seems to have become extinct; in others is above tenfold the size, which would seem necessary for its purpose. — 1791 formsallantoids · more allantoid · most allantoid