weathercock

n. 1. 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. “As a wedercok that turneth his face with every wind.” Chaucer. [ 1913 Webster ]

Noisy weathercocks rattled and sang of mutation. Longfellow. [ 1913 Webster ]

2. Hence, any thing or person that turns easily and frequently; one who veers with every change of current opinion; a fickle, inconstant person. [ 1913 Webster ]