The Collaborative International Dictionary of English v.0.48:

Allantoid \Al*lan"toid\, Allantoidal \Al`lan*toid"al\, a. [Gr. ?
   shaped like a sausage; ? sausage + e'i^dos form.] (Anat.)
   Of or pertaining to the allantois.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Allantois \Al*lan"to*is\, Allantoid \Al*lan"toid\, ] n.. (Anat.)
   A membranous appendage of the embryos of mammals, birds, and
   reptiles, -- in mammals serving to connect the fetus with the
   parent; the urinary vesicle.
   [1913 Webster]

WordNet (r) 3.0 (2006):

allantoid
    adj 1: shaped like a sausage [syn: allantoid, sausage-
           shaped]