The Collaborative International Dictionary
Metadiscoidal
Metadiscoidal \Met`a*dis*coid"al\, a. [Meta- + discoidal.] (Anat.) Discoidal by derivation; -- applied especially to the placenta of man and apes, because it is supposed to have been derived from a diffused placenta.
Wiktionary
metadiscoidal
a. (context anatomy English) discoidal by derivation; applied especially to the placenta of humans and apes, supposed to have been derived from a diffused placenta.