junkyard dog

noun3

1. •
   An aggressive dog which guards a scrapyard or junkyard.
2. •
   An animal or person with an especially nasty and combative demeanor.

   • House minority whip . . . Gingrich has earned enmity in abundance for his junkyard-dog tactics. — 1992
3. •
   A hot dog laden with toppings, such as onions, pineapple, or chili.