(1):

(v. t.) To make sharp, keen, or eager; to excite; to stimulate; as, to whet the appetite or the courage.

(2):

(v. t.) To rub or on with some substance, as a piece of stone, for the purpose of sharpening; to sharpen by attrition; as, to whet a knife.

(3):

(n.) The act of whetting.

(4):

(n.) That which whets or sharpens; esp., an appetizer.