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

Dogs are welcome whether purebred or mutt, mastiff or Chihuahua. —Josh Max, Forbes.com, 18 Apr. 2025

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

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