The term "stepping gas" refers to the action of increasing the speed of a vehicle. Antonyms for this phrase could include "braking," which means slowing down or stopping a vehicle, or "coasting," which refers to allowing a vehicle to move without pressing the accelerator. Another antonym could be "idling," which means the vehicle is running but not moving. Other antonyms might include "reversing," which means moving backwards, or "parking," which means coming to a complete stop and leaving the vehicle. These antonyms are useful for describing different driving behaviors or situations that may require different levels of speed or control.