The term "Bull fly" typically refers to an insect species known as the horse fly. These robust flies are infamous for their painful bites and aggression towards animals and humans alike. However, when searching for synonyms, the term "Horse fly" is the more commonly used alternative for Bull fly. Other synonyms that can be used to describe these insects include gadfly or cleg. These names are often used interchangeably to refer to this pesky insect. Regardless of the term used, it's important to take precautions to protect oneself from their painful bites when venturing outdoors.