In stock market trading, a bull trap is an inaccurate signal that shows a decreasing trend in a stock or index has reversed and is now heading upwards, when in fact, the security will continue to decline.
It is seen as a trap because investors with a "bullish" market sentiment purchase the stock, thinking it will increase in value, but is trapped with a poor performing stock whose value is still falling.
See also
Boom and bust Dead cat bounce Economic bubble Market trend Speculation Stock market bubble
References
Setting the Bull Trap (investorinsight.com) Don’t Fight a Bull Trap (stocks-simplified.com)