ankylosaurus UK /ˌæŋkɪləʊˈsɔərəs/US /ˌæŋkəloʊˈsɔːɹəs/ noun1 •Ankylosaurus magniventris, a large herbivorous dinosaur of the Cretaceous period notable for its heavy armor and clublike tail. formsankylosauri · ankylosauruses