scleractinian /ˌsklɪəɹækˈtɪniən/adjective 1noun 1forms 3 adjective1 •Of, pertaining to, or characteristic of the corals of the order Scleractinia.In the buildup to the big night—the mass spawning always occurs after sundown—the corals begin to “set,” which might be thought of as the scleractinian version of going into labor. — 2014 noun1 •Any of the corals of the order Scleractinia. formsscleractinians · more scleractinian · most scleractinian