sabretoothEnglishOxford Dictionary of Englishsabretooth /ˈseɪbətuːθ / ▸ noun 1 (also sabre-toothed cat or sabre-toothed tiger) a large extinct carnivorous mammal of the cat family, with massive curved upper canine teeth. Several genera in the family Felidae, in particular Smilodon of the American Pleistocene and Machairodus of the Old World Pliocene. 2 a large extinct marsupial mammal of the South American Pliocene, with massive curved upper canine teeth. Genus Thylacosmilus, family Borhyaenidae.