A stock, index, bond, or other financial instrument that signifies, foretells or spearheads the direction of a market, industry or sector. For example, if a share is staging a bullish or bearish trend ahead of other shares, it may be considered to be leading the direction of its industry or sector, and as such it may signal the general trajectory of future prices. Blue chips or widely traded stocks may, at times, become bellwethers of market direction. Generally, when the price of a bellwether stock starts to pick up, this may signify a bullish trend for the overall stock market. In the Treasury bond market, the 10-year note is a bellwether security.

In a different context: compare- a bellwether issue.