Entry 1 sense Webster, 1913 Ornithorhynchus · Or·ni·tho·rhyn·chus · IPA /ˌɔː(ɹ)nɪθəˈɹɪŋkəs/ 01 prop. n. A genus of monotremes including the platypus (Ornithorhyncus anatinus). See Duck mole, under Duck. 1. A genus of monotremes including the platypus (Ornithorhyncus anatinus). See Duck mole, under Duck.(Zool.) See: Duck