The phrase "center armrest" refers to a padded or cushioned support in the middle of the seat in a vehicle. It is used to rest your arm on while sitting so that you can feel more comfortable. Full definition
The front seat center armrest is positioned too far back. (truecar.com)
It also hosts an array of features including rear center armrest with two cup holders, panoramic glass sunroof and roller sun blinds for rear side windows. (cardekho.com)
Five adults can be crowded in, but the large fold - down center armrest and presence of two adjustable headrests do more than hint that the rear seat is really designed for two. (articles.orlandosentinel.com)