AFAIK a bristle brush is one that was made with boar hair... Haven't seen any other brushes than badger (either European or Chinese hog badger), boar, and synthetic. Badger hair is badger hair, bristle is boar (and boar of coarse is boar), and synthetic bristle is crap.
Oh, and come to think of it, one chinese supplier that I know has recently come out with horse/pony hair brushes and knots. Have no idea whether they're worth a thing though.
Henk