to promote (a physiological process) or increase the activity of (an organ)

Chewing stimulates the production of saliva

Fertility drugs were used to stimulate the ovaries

to give mental nourishment or encouragement to (a person, their mind, etc)

You have stimulated my curiosity

I was stimulated to carry out my own researches

to serve as a mental or physiological stimulant or stimulus

His lectures failed to stimulate