When it comes to synonyms for the term "jack russell", there are a few options that can be used interchangeably. One of the most common synonyms is "Parson Russell Terrier", which is a breed of small dog originally bred for fox hunting in England. Another synonym for "jack russell" is simply "jrt", which is an abbreviation commonly used in dog show circles. Finally, the term "fox terrier" is sometimes used as a synonym for "jack russell", though this can refer to a variety of different breeds. Regardless of which synonym is used, all refer to a small, energetic and intelligent breed of dog that is beloved by many pet owners.