(1):

(n.) Hence, any thing or person that turns easily and frequently; one who veers with every change of current opinion; a fickle, inconstant person.

(2):

(v. t.) To supply with a weathercock; to serve as a weathercock for.

(3):

(n.) A vane, or weather vane; - so called because originally often in the figure of a cock, turning on the top of a spire with the wind, and showing its direction.