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

Breeds commonly seen in Milwaukee – such as pit bull mixes, cane corsos and mastiffs – can’t tolerate more than 15 minutes in freezing weather. —Quinn Clark, jsonline.com, 22 Jan. 2026

Jones, 1-year-old mastiff mix, #967270. —Linda McIntosh, San Diego Union-Tribune, 22 Dec. 2025

Suarez advises keeping in mind that certain breeds are more likely to have chronic and expensive medical conditions that require veterinary care, including French bulldogs, and some larger breeds of dogs such as mastiffs and Great Danes. —Terry Ward, USA Today, 1 Dec. 2025

Bedell said, depending on the type of mastiff, these canines can sleep between 16 and 20 hours daily. —Liz O'Connell, MSNBC Newsweek, 25 Nov. 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