junkyard dog

From junkyard +‎ dog. The literal sense was popularized by the song Bad, Bad Leroy Brown (1973) by Jim Croce (see citation below).

• Audio (General Australian):

  (file)

junkyard dog (plural junkyard dogs)

1. (literally) An aggressive dog which guards a scrapyard or junkyard.
   • 1936 July 23, “Dan D. Lyon”, in Scranton Republican‎^[1], page 4:

     I saw nine dogs running en pack on South Washington Avenue ... They were making for a junkyard that appeared to be their headquarters ... And those junkyard dogs do make nights hideous for the neighbors

2. (idiomatic, by extension) An animal or person with an especially nasty and combative demeanor.
   • 1973 Jim Croce, "Bad, Bad Leroy Brown", from the album Life and Times (song lyrics):

     Badder than old King Kong / And meaner than a junkyard dog

   • 1992 September 21, Janice Castro, “With Friends Like These ...”, in Time:

     House minority whip . . . Gingrich has earned enmity in abundance for his junkyard-dog tactics.

   • 2004, Peter Maravelis, San Francisco Noir, →ISBN, page 50:

     "I'm gonna hire me a lawyer," he said. "A real junkyard dog."

3. A hot dog laden with toppings, such as onions, pineapple, or chili.

• “junkyard dog”, in OneLook Dictionary Search.