A "generator unit" refers to a machine or device that creates electrical energy. It usually runs on gas, diesel, or steam, and its primary purpose is to produce electricity. Full definition
In the engine compartment diagram, we see a coolant reservoir for a «motor generator unit,» which confirms the available mild hybrid system. (automobilemag.com)
The engineers focused on making the motor - generator unit as efficient as possible. (thetorquereport.com)
Then, as the vehicle comes to a stop, the motor - generator unit spins the engine, bringing it to a smooth stop — properly positioned for a smooth restart. (thetorquereport.com)