The term 'Fuel Rating Word' is referring to the octane rating of a fuel, which is a measure of the fuel's ability to resist 'knocking' or 'pinging' during combustion. Octane ratings are typically expressed as a number, such as 87 or 93, and indicate the fuel's ability to resist pre-ignition. Higher octane ratings indicate higher levels of resistance to pre-ignition, and therefore better performance in engines.