weathercock

[weth -er-kok] /ˈwɛð ərˌkɒk/
noun
1.
a weather vane with the figure of a rooster on it.
2.
(loosely) any weather vane.
3.
a person who readily adopts the latest fads, opinions, etc.:
The count is the weathercock of the jet set.
Origin
1250-1300; Middle English wedercoc. See weather, cock1
British Dictionary definitions for weathercock

weathercock

/ˈwɛðəˌkɒk/
noun
1.
a weather vane in the form of a cock
2.
a person who is fickle or changeable
verb
3.
(intransitive) (of an aircraft) to turn or tend to turn into the wind