Mas"tiff (?), n.; pl. Mastiffs (). [Mastives is irregular and unusual.] [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. matin mastiff, OF. mastin.] Zool.
A breed of large dogs noted for strength and courage. There are various strains, differing in form and color, and characteristic of different countries.
Mastiff bat Zool. , any bat of the genus Molossus; so called because the face somewhat resembles that of a mastiff.
© Webster 1913.