Discoid :: Discoid (a.) Having the form of a disk, as those univalve shells which have the whorls in one plane, so as to form a disk, as the pearly nautilus..
Discoid :: Discoid (n.) Anything having the form of a discus or disk; particularly, a discoid shell..
Metadiscoidal :: Metadiscoidal (a.) Discoidal by derivation; -- applied especially to the placenta of man and apes, because it is supposed to have been derived from a diffused placenta..