something that rouses or incites to action or increased action; incentive
Physiol., Psychol. any action or agent that causes or changes an activity in an organism, organ, or part, as something that excites an end organ, starts a nerve impulse, activates a muscle, etc.
Something causing or regarded as causing a response.
An agent, action, or condition that elicits or accelerates a physiological or psychological activity or response.
Something that incites or rouses to action; an incentive: “Works which were in themselves poor have often proved a stimulus to the imagination”(W.H. Auden).