noun

• (archaic) A dog that has been tied up; a mastiff or other kind of guard dog.
  "The horsemen spreading themselves along the side of the cover, waited untill the keeper entered, leading his ban-dog; a large blood-hound tied in a leam or band, from which he takes his name."
• (specifically) A type of large, ferocious dog, bred by crossing American pit bull terriers with Neapolitan mastiffs.
• (figurative, literary) Something that or someone who pursues doggedly.
  "He escaped from that experience confounded, horrified, and conscious of degradation. Those infernal bandogs of the law had treated him as a piece of insensate property to their drivelling mumbo-jumbo, as if mere contact with it had robbed him of all rights to the dignity and integrity of his own ego."
• (obsolete, slang, cant) A bailiff or prison guard.