Bulldog

Part of speech: noun (n.)

1. A variety of dog, of remarkable ferocity, courage, and tenacity of grip; -- so named, probably, from being formerly employed in baiting bulls.

2. A refractory material used as a furnace lining, obtained by calcining the cinder or slag from the puddling furnace of a rolling mill.

Part of speech: adjective (a.)

Characteristic of, or like, a bulldog; stubborn; as, bulldog courage; bulldog tenacity. Bulldog bat (zo'94l.), a bat of the genus Nyctinomus; -- so called from the shape of its face.