The answer is: using shaving cream, rather than shaving on dry skin.
Friction is the force resisting the relative motion of solid surfaces, fluid layers and material elements sliding against each other.
Shaving would be much easer using shaving cream, because friction is decreased.
This is example of decreasing skin friction.
Skin friction is the force resisting the motion of a fluid across the surface of a body.
Other examples cause increase of friction.
