Junkyard Dog Meaning

(idiomatic, by extension, hyphenated when used attributively) An animal or person with an especially nasty and combative demeanor.

Example: 1992, Janice Castro, "With Friends Like These ...," Time, 21 Sept.:
  House minority whip . . . Gingrich has earned enmity in abundance for his junkyard-dog tactics.
2004, Peter Maravelis, San Francisco Noir, ISBN 9781888451917, p. 50:
  "I'm gonna hire me a lawyer," he said. "A real junkyard dog."
A hot dog laden with toppings, such as onions, pineapples, or chili