A substance that raises levels of physiological or nervous activity in the body. Caffeine is a common stimulant found in coffee and tea.
An agent, especially a drug, that temporarily quickens some vital process or the functional activity of some organ or part. The doctor prescribed a stimulant to help with the patient's attention deficit disorder.
Something that incites or quickens action, feeling, or thought. The motivational speaker served as a stimulant for the team, inspiring them to achieve their goals.