to provide someone/something with the substances and nutrients they need to grow and maintain their condition and health, often in the form of food;
e.g. It is important to nourish children well so that they can grow and develop healthy bodies.
(verb)
broadly, to promote the growth and development of something/someone;
e.g. The fertile soil will nourish the crops and allow them to flourish.
(verb)
broadly, to support or maintain something and allow it to remain in its condition or grow, especially describing a belief or feeling that stays on one's mind for a long time;
e.g. I helped her nourish her dream of traveling the world.