(1):

(n.) One who, or that which, forwards, advances, or promotes; an encourager; as, a promoter of charity or philosophy.

(2):

(n.) One who excites; as, a promoter of sedition.

(3):

(n.) Specifically, one who sets on foot, and takes the preliminary steps in, a scheme for the organization of a corporation, a joint-stock company, or the like.

(4):

(n.) An informer; a makebate.