protoceratopsPronunciation: /ˌprəʊtə(ʊ)ˈsɛrətɒps/Definition of protoceratops noun a small quadrupedal dinosaur of the late Cretaceous period, having a bony frill above the neck and probably ancestral to triceratops. Genus Protoceratops, infraorder Ceratopsia, order Ornithischia protoceratops in other Oxford dictionaries Definition of protoceratops in the US English dictionary