A breeding ground can be defined as a place or situation that fosters the growth or development of something, particularly something undesirable. There are a few synonyms that can be used in place of breeding ground, such as hotbed, incubator, and nursery. Hotbed refers to a situation where something is thriving or growing rapidly. Incubator refers to a controlled environment where something is developed or grown, much like a laboratory. And nursery is a specific word often used to describe a place where young or new plants are grown, but can also apply to animals or humans. Each of these synonyms can be used to describe a situation or place where a particular idea, behavior, or organism is flourishing.