mastiff Meaning, Definition & Usage

  1. noun an old breed of powerful deep-chested smooth-coated dog used chiefly as a watchdog and guard dog

WordNet

Mas"tiff noun
Etymology
Prob. fr. Prov. E. masty, adj., large, n., a great dog, prob. fr. mast fruit, and hence, lit., fattened with mast. There is perh. confusion with OF. mestif mongrel; cf. also F. mâtin mastiff, OF. mastin.
Wordforms
plural Mastiffs [Mastives is irregular and unusual ]
Definitions
  1. (Zoöl.) A breed of large dogs noted for strength and courage. There are various strains, differing in form and color, and characteristic of different countries.

Webster 1913