"Competing" is a human concept. Wild animals compete for survival, but not for trophies like we ask them to.
To a dog, performing a task is working.
French ring? Working.
Hiking with loaded side bags? Working.
Search and rescue? Working.
Playing fetch? Working.
To me, a "working dog" is one that came from bloodlines with a long, established history of being suitable for serious physical tasks (schutzhund, search and rescue, etc.), having a solid temperament, and high drive.