A breed of large dogs noted for strength and courage. There are various strains, differing in form and color, and characteristic of different countries.
I had less apprehension concerning the dogs, whereof three or four came into the room, as it is usual in farmers’ houses; one of which was a mastiff, equal in bulk to four elephants, and another a greyhound, somewhat taller than the mastiff, but not so large.
Jonathan Swift. Gulliver's Travels Into Several Remote Regions of the World (1726)
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Lilliput and Brobdignag being, in my creed, solid parts of the earth’s surface, I doubted not that I might one day, by taking a long voyage, see with my own eyes the little fields, houses, and trees, the diminutive people, the tiny cows, sheep, and birds of the one realm; and the corn-fields forest-high, the mighty mastiffs, the monster cats, the tower-like men and women, of the other.
Charlotte Brontë. Jane Eyre (1847)
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“ ‘Well, then, you know now. And if you ever put your foot over that threshold again’—here in an instant the smile hardened into a grin of rage, and he glared down at me with the face of a demon—‘I’ll throw you to the mastiff.’
Arthur Conan Doyle. Sherlock Holmes: The Adventure of the Copper Beeches
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an old commissionaire who had been attached to the outdoor service of the hôtel for many years—a grey-haired man, wiry as a terrier and strong as a mastiff.