The word "seatback" refers to the backrest or the upright part of a seat, usually found in vehicles like cars, airplanes, or movie theaters. It is the part of the seat that supports your back while sitting. Full definition
Similar to the Sixty Special Brougham's package of the same name, it featured velour upholstery, Deluxe padded doors, front seatback storage pockets, deep pile carpeting, floor mats, see - through standup hood ornament and vinyl tape accent stripes. (en.wikipedia.org)
Available comfort features include dual - zone automatic climate control with air filter and rear - seat vents, leather - trimmed multi-stage heated front seats with seatback pockets, and a Smart Key System on front doors and trunk with Push Button Start and remote illuminated entry. (novatotoyota.com)