bulldog

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A dog of a breed originally developed in England for bullbaiting, having a short stocky body, large head, and strong square jaws with dewlaps.
• noun A short-barreled, large-caliber revolver or pistol.
• noun A heat-resistant material used to line puddling furnaces.
• noun Chiefly British A proctor's assistant at Oxford University or Cambridge University.
• adjective Relentless or stubborn.
• transitive verb To throw (a calf or steer) by seizing its horns and twisting its neck until the animal falls.

from The Century Dictionary.

• noun Same as bulldog ant.
• noun A variety of dog of comparatively small size, but very strong and muscular, with a large head, broad muzzle, short hair, tapering smooth tail, and remarkable courage and ferocity. Dogs of this kind were formerly much used in bullbaiting, whence the name.
• noun A bailiff.
• noun The assistant or servant who attends the proctor of an English university when on duty.
• noun A pistol; in recent use, a small revolver with a short barrel carrying a large ball.
• noun Nautical: The great gun in the officers' wardroom cabin.
• noun A general term for main-deck guns.
• noun In metallurgy, tap-cinder from the puddling-furnace, after the protoxid of iron has been converted into sesquioxid by roasting.
• noun A name given by the Canadian half-breeds to the gadfly.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) A variety of dog, of remarkable ferocity, courage, and tenacity of grip; -- so named, probably, from being formerly employed in baiting bulls.
• noun (Metal.) A refractory material used as a furnace lining, obtained by calcining the cinder or slag from the puddling furnace of a rolling mill.
• adjective Characteristic of, or like, a bulldog; stubborn.
• adjective (Zo'94l.) a bat of the genus Nyctinomus; -- so called from the shape of its face.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A breed of dog developed in England by the crossing of the bullbaiting dog and the Pug to produce a ladies companion dog. Having a very smooth coat, a flattened face, wrinkly cheeks, powerful front legs and smaller hind legs.
• noun A shortened form of British bulldog.
• noun A stubborn person.
• verb transitive To chase (a steer) on horseback and wrestle it to the ground by twisting its horns (as a rodeo performance).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb attack viciously and ferociously
• noun a sturdy thickset short-haired breed with a large head and strong undershot lower jaw; developed originally in England for bull baiting
• verb throw a steer by seizing the horns and twisting the neck, as in a rodeo