- any of various groups of mammallike reptiles of the extinct order Therapsida, inhabiting all continents from mid-Permian to late Triassic times, some of which were probably warm-blooded and directly ancestral to mammals.
- of or relating to the Therapsida.
- any extinct reptile of the order Therapsida, of Permian to Triassic times: considered to be the ancestors of mammals
