di·din·i·um \dīˈdinēəm\noun Etymology: New Latin, from di- + Greek deinos terrible + New Latin -ium — more at din- 1.capitalized: a genus of carnivorous protozoans (order Holotricha) that feed on paramecia 2.pluraldidiniums\-mz\ordidin·ia\-nēə\: any protozoan of the genus Didinium