The phrase "thumb rest" refers to a small area or indentation on a device or object that is designed to give your thumb a place to rest comfortably while using it. Full definition
It's simply the perfect width to hold between two hands while typing or watching video, and the wide front bezels work well as thumb rests. (mobilesyrup.com)
We took great pleasure in the large thumb rest option which gives you an excellent place to tuck your thumb away while gaming and still have excellent access to the side buttons. (pocket-lint.com)
The center console is angled for a driver - focused approach, and the leather - wrapped steering feels great to hold with good thumb resting points. (indianautosblog.com)