Of the many marketing terms found on the front of skincare product labels, this is one of the most meaningless. 'Nourishing' the skin is medical absurdity. The use of the term is meant to lead the consumer to believe that the nourishig skincare product provides food or other substance necessary for skin growth. Marketing nonsense.
Skincare products are applied on the surface of the skin and are in contact with the outer 15-20 cell layers. These superficial layers of skin are comprised of non-living, yet functional, dead cells. It is not medically possible to 'nourish' dead tissue. Skin is 'nourished' from its blood supply in the much lower layers of skin.
As an organ, healthy skin parallels a healthy body. Healthy, nourished skin is a result of a nutritious diet, rich in fruits, vegetables, lean protein, and healthy carbs, adequate sleep, exercise, and the avoidance of the stressors that science has shown to be harmful to good skin health, like smoking and utraviolet light exposure. There is no scientific meaning to word 'nourishing' on a skincare product label.