The term 'Passenger Seat' can be summarized by the crossword solution 'PILLION, ' which is a seven-letter word. PILLION is a noun that refers to a seat behind the rider of a horse, motorcycle, or other vehicle. It is also used to describe a person who rides on such a seat. Historically, PILLION was used to refer to a woman riding behind a man on a horse, but today it is used to refer to any passenger riding behind the driver.