The term "backseat" refers to the rear area of a vehicle where passengers typically sit. However, there are several synonyms that can also be used to describe this area. One commonly used term is "rear seat," which refers to the seats at the back of a vehicle. Another synonym is "second row," which is often used to describe the seats immediately behind the front seats. "Passenger compartment" is a more general term that can be used to refer to the entire area of a vehicle where passengers sit, including the backseat. Finally, "rear bench" is a term that specifically describes a long seat spanning the width of the backseat area.