A neutral grip is one that doesn't cause the gun (front sight) to shift right or left on the shot. The front sight will rise under recoil, but it will stay centered in the rear notch.
A neutral grip is where the front sight returns - on it's own - to it's starting position after recoil.
The muzzle (and front sight) may naturally rise a bit to the right, but the important part of a neutral grip is that the front sight will consistently come back down to form a good sight picture without you having to force it.