mastiff

noun

mas·​tiff ˈma-stəf 

: any of a breed of very large massive powerful smooth-coated dogs that are apricot, fawn, or brindle and are often used as guard dogs

Illustration of mastiff

Examples of mastiff in a Sentence

Recent Examples on the Web

Spanish mastiffs, meanwhile, are also known for being hugely affectionate towards family, and a fierce defender of livestock as a working dog. —John W. Dean, MSNBC Newsweek, 7 Apr. 2025

Anthony Devlin / Getty Images Miuccia emerged victorious, beating Ana, a Jack Russell terrier; Liza, the miniature schnauzer; Viking, the Tibetan mastiff; Shake, the Australian shepherd; Sophia, the papillon; and Suzie, the cocker spaniel. —Mithil Aggarwal, NBC News, 10 Mar. 2025

Those breeds include the Bernese mountain dog and mastiffs. —Krystal Nurse, USA TODAY, 21 Feb. 2025

First-round competitor Brina, for instance, is a 158-pound (71.6 kilogram) Neapolitan mastiff. —Jennifer Peltz, Chicago Tribune, 12 Feb. 2025

Word History

Etymology

Middle English mastif, from Medieval Latin mastivus, from Vulgar Latin *masuetivus, from Latin mansuetus tame — more at mansuetude

First Known Use

14th century, in the meaning defined above

Kids Definition

mastiff

noun

mas·​tiff ˈmas-təf 

: any of a breed of large powerful smooth-coated dogs often used as watchdogs and guard dogs