When a security or a class of assets sees its market-driven price move in the opposite direction of the broad market or its competition. The move could be in either direction, but generally occurs as a result of good performance in the face of negative broad market performance.

The meaning is often extrapolated out from just asset prices to business and market fluctuations. If a company is recording increased sales while its competitors lose business, that company would be "bucking the trend".






Taobiz explains Buck The Trend
It may be a bullish signal when a stock is able to resist a prevailing downtrend in its own industry or against the broad market. This suggests that investors are attracted to the stock despite negativity surrounding its competitors and peers.