You may really start something asking for the definition of this term --- because different people have different notions about what it means.    
To me - it just means a person who is just breeding a pet -- and not being very professional about doing it.    
A lot of people who breed their pet or pets are very professional and do an excellent caring job -     
Other people just take their little females, find a stud, and get a litter that they plan to sell.  (These are the ones that I refer to as backyard breeders.)  I think the term refers to people who aren't as professional and caring as anyone who breeds dogs should be.     
The term "backyard" - itself - implies that the dogs and puppies aren't kept inside and socialized with the family.  We Yorkie owners are "frontroom" or "bedroom" breeders...... our dogs and their puppies are beloved members of our family.       
Carol Jean        |