Bulldog

Bull·dog

Bulldog

n.
  1. A variety of dog, of remarkable ferocity, courage, and tenacity of grip; -- so named, probably, from being formerly employed in baiting bulls. (Zool.)
  2. A refractory material used as a furnace lining, obtained by calcining the cinder or slag from the puddling furnace of a rolling mill. (Metal.)

Bulldog

a.
  1. Characteristic of, or like, a bulldog; stubborn; as, bulldog courage; bulldog tenacity.

Phrases & Compounds
Bulldog bat
a bat of the genus Nyctinomus; -- so called from the shape of its face.