† polyplacidadj. [ < poly-comb. form + ancient Greek πλακοῦς flat cake, tablet (see placentan.) + -idsuffix1] ZoologyObsoleterare (of an echinoderm) having more than one madreporite.Apparently only attested in dictionaries or glossaries.
ΚΠ
1890 Cent. Dict. XVI. 4607/3Polyplacid, having more than one madreporic plate, as a starfish; not monoplacid.