weathercock

From Middle English wetharcoke, weþercok, wedercoc, wederkok, equivalent to weather +‎ cock.

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weathercock (plural weathercocks)

1. A weather vane, sometimes in the form of a cockerel.
2. (figuratively) One who veers with every change of current opinion; a fickle, inconstant person.
3. (chiefly Canada, US) A kind of wind pump whose top behaves like a weather vane, moving with the wind direction, but which also has a wheel attached to measure wind speed.

• weathervane, weather vane
• windsock, wind sock

weathercock (third-person singular simple present weathercocks, present participle weathercocking, simple past and past participle weathercocked)

1. (intransitive, of a boat) To turn upwind because of the difference in water pressure on two sides.
2. (intransitive, of an airplane or missile) To veer into the direction of the oncoming (relative) wind.
3. (transitive) To act as a weathercock for.