any of an order (Milleporina) of coral-like hydrozoans that form branching or leaflike calcareous masses with small openings on the surface
See millepore in American Heritage Dictionary 4
(mĭlˈə-pôrˌ, -pōrˌ)
noun
Any of various reef-building hydrocorals of the order Milleporina of tropical marine waters, forming white or yellowish calcareous structures and resembling the true corals of the class Anthozoa.