A zone fossil refers to a species of organism that is commonly found in a particular geologic zone. However, there are other words and phrases that can be used to describe this concept. Some synonyms include index fossil, guide fossil, key fossil, and stratigraphic marker. All of these terms refer to a type of fossil that is used to determine the age and relative position of rock layers. The use of zone fossils and their synonyms is crucial in the field of geology, as they allow scientists to study the Earth's history and the evolution of life on our planet.