Definitions

1. adjective

relating to or characteristic of monotremes, a group of mammals that lay eggs

“Monotremal mammals, like the platypus and echidna, have unique characteristics that set them apart from other mammals.”

2. noun

a monotreme or an animal that lays eggs, especially a platypus or echidna

“The zoo has a collection of monotremal species, including platypuses and echidnas.”