(1):

(n.) A state of aroused or increased vital activity in an organism, or any of its organs or tissues.

(2):

(n.) The act of exciting, or the state of being roused into action, or of having increased action; impulsion; agitation; as, an excitement of the people.

(3):

(n.) That which excites or rouses; that which moves, stirs, or induces action; a motive.