"Yaw would be motion about the z axis or "normal axis" i.e. the axis of rotation would be through your head to your feet. I see no way to impart a spin with a single gimbaled motor about this axis, unless it uses a vane to react with the thrust."

"A good analogy Alex, I am thinking a balancing robot has related sensors and code. How about yaw?"

"How exactly do these platfroms "fly" ? Can a single rocket engine gimbal to provide thrust about the lateral and longitudinal axis, yaw and still remain stable while asceding/decending?"