(1):

(a.) Produced increased vital action in the organism, or in any of its parts.

(2):

(a.) Serving to stimulate.

(3):

(n.) That which stimulates, provokes, or excites.

(4):

(n.) An agent which produces a temporary increase of vital activity in the organism, or in any of its parts; - sometimes used without qualification to signify an alcoholic beverage used as a stimulant.