monotreme /ˈmɒnətɹiːm/adjective 1noun 1forms 1 adjective1 •Having a single trema, or aperture.Nomotreme fern and moss spores are monotreme. — 1952 noun1 •Any of the order Monotremata of mammals that lay eggs and have single orifices for urogenital and digestive functions (cloaca); an echidna, platypus or one of their extinct relatives. formsmonotremes
