A weathervane is a device that shows which direction the wind is blowing. You've probably seen one on top of a barn or church: a metal arrow or decorative figure (often a rooster) that spins freely on a rod. When the wind blows, the weathervane turns to point in the direction the wind is coming from.

Weathervanes have been used for thousands of years, helping farmers, sailors, and anyone who needed to predict weather patterns. In the days before weather apps and satellites, knowing wind direction was crucial: winds from the west might bring rain, while winds from the north could signal cold weather approaching.

The word is also used metaphorically to describe someone who constantly changes their opinions to match whatever's popular at the moment. If a politician keeps switching positions based on poll numbers, critics might call them a weathervane, suggesting they turn whichever way the wind blows rather than sticking to their principles. It's not a compliment: it means someone lacks the courage to stand firm when their views become unpopular or inconvenient.