HydrocoralliaHy`dro*co*ral"li*a\, n. pl. [NL. See Hydra, and Coral.] (Zo["o]l.) A division of Hydroidea, including those genera that secrete a stony coral, as Millepora and Stylaster. Two forms of zooids in life project from small pores in the coral and resemble those of other hydroids. See Millepora.